The short answer is that it is never too late. You could conceivably review a session that happened 10 years ago, provided all parties were of legal age, the account is true, and it doesn't veer into any forbidden subjects.
If you want the review to count toward Premium Access credit here, though, there are a few more rules to follow. I'd suggest taking a look
here for details. One of our helpful moderators might jump in, too.