Computer tab -> Search Inventory -> New Advanced Computer Searches

Select the relevant criteria and display columns.
You can then export to a CSV and sort by last check-in date.

if all you need initially is a report, using the Advanced Computer Search section should yield what you want.

Use the following criteria options to see if it gets you what you want

( Last Check-in | less than x days ago | 91 )

and

Operating System | like | 10.6

or

Operating System | like | 10.7

Note that there are parenthesis around the Last Check-in section. Without that you may not get the results you expect in my experience.

If you have OSes going back further than 10.6, you may need to add in some Operating System sections with the general OS version, like 10.5, etc. (Remember to put an "or" between them). Hopefully you don't have Macs running that old of an OS though.

Mike shouldn't parenthesis be on the OS criteria like this:

 Last Check-in | less than x days ago | 91

and

( Operating System | like | 10.6

or

Operating System | like | 10.7 )

@bpavlov I suppose it could go either way, but I just built a quick query as I outlined above and it gave me all Macs with checks ins within 90 days and running 10.6.x or 10.7.x. So, more than one way to skin a cat I guess.

Great, thanks guys. It's all gradually coming back to me... ;)

@mm2270 We do still have a couple of Macs running 10.5.8! There's no defined life cycle for the computers, hopefully we can weed out a few of the dinosaurs that won't be capable of running 10.8...