Breakin of woofer and stability in TS.

Although breakin of speaker is debated subject. I found that it makes sense to breakin the woofer before its used.

As I received a pair of woofer, they were put for breakin. After 12 hours its resonance frequency changed from 70Hz to 54Hz. I left them untouched for 24Hrs. And again measured its resonance frequency. Now the the resonance frequency was 66Hz.
From what was experienced, I think , the TS of unused drivers are different from the warmedup drivers. we need to breakin everytime before we measure the TS. because while listening to music the TS would change. and if we design woofer without warmup, the speakers might not sound really good after a couple of minutes.

what procedure do you follow? pl share your experience.