If you do most of your drilling here, 7sage shows you which PTs are still "clean" and completely untested, and also shows you how many questions you've seen from each PT (if applicable). Because of this, I know they pull from the earliest tests first, to keep more recent PTs fresh.

That said...

The actual LSAT will have questions that feel very familiar. You haven't seen them before, but you've seen the exact structure or topic or both. I, too, wanted to save "fresh" PTs as long as possible, but after taking the real thing, I realize the newness doesn't matter nearly as much as mastering the question types and practicing the time constraints. If anything, that feeling of "I already answered this one" is more realistic, not less.