Only if you replace a driver or crossover, as far as I know. What you probably experienced is the speaker cables and internal wiring just got re-acquainted.
Do you ever have to re-break-in speakers?
Odd question but I recently purchased a barely used pair of speakers. I'm sure he listened to them long enough to break them in but then he moved to another model and they sat for quite a while before I purchased them. I've listened to them for a few weeks now and I swear they sound better now. Do new-ish speakers stiffen up again if left unused for a long period of time? Or are my ears just getting used to them?