Hi,
Currently supporting segmentation through the API is an open feature
request.
But through the UI, we do expose a days to transaction dimension. You
could also user the user-defined value or even an event to capture the
date of when the person joined. The tricky part of all these methods
is that GA treats dimensions as strings. So you'll have to build some
sort of reg ex to match the greater than 60 as a number.
-Nick