Obviously trying to get old versions of software from a software company doesn't usually work out when you try to ask them "hey could we have all of your software versions for software archival?" so WHY NOT DO IT OURSELVES?!
In case you don't know what Trillian is, click here.
The amount of builds per version (At least past 5.4 from what I can tell) is determined by the changelogs available for that version of Trillian. Usually the last changelog indicates how many builds there are for that version, but it's not always correct.
for future reference.