Axiom has stated that their speakers do not require break-in nor that the sound characteristics change over time due to use.

Your room/placement, volume, any processor settings enabled and the quality of the recording you are playing through your speakers at the time will be the biggest determinants on the perceived quality of sound. Psychoacoustics is another important factor to take into consideration when judging a speaker over time.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne