My rule of thumb now-a-days is I only do follow up reviews if I have something major to say. I don't do them just to say "I still use it all the time" or anything like that. If I learn something new about it, find a new way to use it, find a major flaw over time, or have something important to add... then I'll do them. Otherwise, I just let the original review stand for itself.
A reminder is usually emailed after 2 months to do the follow-up. If I don't have anything useful to add, I just ignore the reminder.