I use FREE when I no longer need the table but the modular unit I'm currently in continues for a while.
I follow the same principle. If it's the end of the "block" then I just let "god sort 'em out", but if it's in the middle then I use FREE.
If data volume is not large then even not using FREE most likely won't be noticeable. I'm guessing that's why many ABAPers don't bother with it.
I'm curious though if we need to start being more cognizant about the memory usage since HANA runs, you know, in memory. 