Dear John,

We thank you as well as the referee for the additional comments 
on our manuscript.  We are pleased to resubmit our manuscript ApJL #21952 
in modified form with this response.  We have addressed these final comments 
and hope that our manuscript can be accepted in its current form. 

Regarding the discussion on stellar ages, we thank you for sharing 
your thoughts.  We regret that you found our reply to your note 
perplexing.  We have tried to respond honestly and diligently 
to alleviate your concerns.

The age calibration of Donahue (1993; 1998) and the efforts of
our group are based on anchors provided by the turn-off
ages of open clusters.  Donahue (1993; 1998) utilizes
the Pleiades, the Hyades, Mel 111 (Coma Ber), NGC 752, 
and M 67, for calibration in the age range from 
< 100 Myr to > 1 Gyr.  Our upcoming effort will
improve upon this work by including updated
cluster ages, as well as detailed discussions of the methodology 
and uncertainties.  We agree that it would be beneficial to 
include more star clusters of intermediate age in this calibration, 
however this is not the subject of the present paper.  The internal
consistency test applied by Donahue (1998) to a subset
of binaries in his work suggested errors of order 50 %,
similar to the dispersion in the relation of Soderblom
et al. (1991).   It is difficult to see how fundamental
revisions in stellar evolution theory could systematically
change the ages of open clusters by more than x2. 
Gallart et al. (2005) indicate systematic errors up to 30 % 
for turn-off ages derived from color-magnitude diagrams 
of intermediate age clusters (1-3 Gyr; see their Figure 3), 
and more like 10 % at older and younger ages.  However, as you 
point out, more work is needed. 

In this submission of the present paper, we have changed the 
reference to our main sequence age calibration to 
Donahue (1998) and omit reference to Barnes (2007).  

In the first full paragraph of section 2, the seventh sentence 
now reads: 

"Ages for these stars were estimated from calcium
H & K emission-line indices which trace stellar
activity levels using the calibration of Donahue
(1998).  Errors in age for both the young stellar
populations as well as the main sequence stars are
estimated to be < 50 %, though the uncertainties in
absolute calibration of these ages are not well understood."

We hope you find this text acceptable.  Our ultimate goal, is 
to report these results to the community accurately, and as 
soon as possible.

Best wishes,
Michael Meyer

*****************Response to the Referee*************************************

We thank the referee for her/his most recent comments. 
Our responses to each point are given below.  

In addition, we bring to the referee's attention one final 
change to the manuscript.  In response to further comments from 
the editor, we have: a) changed the reference to the source of the
calibration of our main sequence stellar ages from Donahue (1993) 
to Donahue (1998); b) clarified the magnitude of random uncertainties 
in the ages; and c) commented on the uncertainties in the absolute
calibration of these ages. 

######################################################################

REFEREE:  The discussion of uncertainties is much clearer. However I still 
find the "minimum uncertainties of less than 1%" wording on pages 3 and 4 
confusing.  Are these uncertainties more or less than 1%? It is also not 
clear from the sentence on page 5 "As a result, the errors quoted..." 
exactly how the errors given in Table 1 are calculated. For example, does 
this figure add in quadrature the uncertainty in (F8/F24)phot, which is 
4.3%, and the uncertainty in (F24/F8)obs, which is 1-2%?

ANSWER:  We have simplified the text to read "minimum uncertainties of 1 %"
when describing the random errors in the IRAC and MIPS data.  We have also 
attempted to clarify the sentence to which the referee refers at the end 
of the first full paragraph in section #3. 

"As a result, the errors quoted on the reported excesses include
the internal (random) errors in the MIPS24/IRAC8 ratio (typically 1-2 %), 
as well as the dispersion in our estimate of the photospheric color
(4.3 %) rather than the error in the mean, added in quadrature."

REFEREE:  "Figure 3" should be "Figure 2" on page 5.

ANSWER:  Corrected.  We apologize for the error. 

REFEREE:  On page 6 the transition timescale is quoted as a^1.5 sigma^-1 
which is used to infer a range of x3 in time from a range x2 in radius. 
However, sigma is also a function of radius. Thus the formulation of the 
same equation by Kenyon & Bromley as a^3 (sigma_0/sigma_MMSN)^-1 is more 
appropriate here, and a range x2 in radius gives a range x8 in time. 
This is more consistent with the range of time that 24micron excess is 
apparent in the Kenyon & Bromley 2004 models for a x2 radius range, 
which suggest that 24micron emission from terrestrial planet formation 
should persist on timescales longer than the age range of the bins. 
The same models also show that 24micron emission can trace material at 
1AU, whereas 4-7AU is quoted in this paper, implying that the range in 
radii probed by 24micron observations is in fact much larger, x7 or more. 
Thus while I agree that some models for disk evolution may allow
the fraction of stars with excess to be summed between 3-300Myr 
(and that it is worthwhile pointing out this possibility), this is not 
demonstrated with the present argument.

ANSWER:  We thank the referee for pointing out the confusion in 
our arguement.  Rather than adopting a minimum mass solar nebula
model with sigma going as a^(-1.5) as in Kenyon and Bromley
(2004), we now reference Kitamura et al. (2002) who derive
a range from [-1,0] for the exponent in the mass surface density 
profile for disks surrounding T Tauri stars studied through 
mm-wave interferometry.  Using this form in our expression, 
a range of x2 in radius corresponds to a range of x 3-6 in 
time which we now report.  We have revised the text to suggest
that the emission "...should not persist over timescales much 
larger than our age bins".  Regarding the range of radii from 
which we can observe 24 micron emission, the Kenyon and Bromley
result quoted above is for dust that emits at both 10 and 20 
microns (i.e. warmer dust at smaller radii), whereas our results 
are focused on sources that exhibit excesses at 24 microns, 
but not at shorter wavelengths.  We now make this clear in the 
text in paragraph 2 of section 4.  Although the present arguement 
may still be considered weak, we agree with the referee that it 
is valuable to point out the possibility that summing the 
fractions in figure 2 may be appropriate.  We think this is 
in the spirit of the Letters format where such a discussion
may be considered timely to report to the community even if
the basis for the arguement is difficult to justify in a 
quantitative way.