Do you think driver “break in” is real?

Do you think “high end” drivers and crossovers typically need a “break in” period before they sound their best?  I ask because, I believe I’ve experienced this first hand in a very significant way. I replaced the tweeters (same exact brand and model as original) in my ACI Sapphire 25 year anniversary edition speakers and for the first week I thought I’d lost my all time favorite speakers. I was depressed!  So I just kept playing them…  finally after a couple weeks, I’m literally stunned and blown away at how incredible these speakers sound. Completely different than the first 30 or 40 hours after I put in the new Scan Speak tweeters. So I say break in period must be real - at least for some drivers. Has anyone else experienced this to a degree that is unmistakeable?  
Crossovers too?  I just rebuilt the crossovers for a pair of ACI Sapphire XL’s (using highest quality components- same values) and so far they sound mediocre. Hoping for the same result as my other Sapphires but after about 20 hours - no noticeable difference - and they do not even sound as good as prior to crossover rebuild. They sound flat, too bright with poor imaging - but for 10 to 15 years they were pretty great sounding speakers. Thoughts on crossover break in?? 
Thanks to anyone who responds!!  


Part of the myth is so you won't return it immediately and you'll get used to the sound of your new speaker

I can't imagine getting used to a speaker I don't like. I can imagine a speaker growing on me though that I like from the moment I hook them up.

there is no way I would argue a point that most people believe as it sure won't change anyone's mind.  Whether it happened or not, my stuff never changed in sound if it did.

Absolutely real. I once had to replace the diaphragm on one of my previous horn tweeters; well the fixed channel was harsh and piercing for a couple days, skewing the stereo image to that side, until it settled down and both channels started playing equal.

Same with my new tweeters, I had to change the crossover settings after a few days because they started really hot and bright fresh out of the box and ended up smooth to the point of dullness until I changed the settings again.

@willywonka come on... it's one of the easiest things to verify. 

Just put in a brand new tweeter on one side, and keep the old, used tweeter on the other side, and see if you can get any decent center image. I guarantee you won't! And you can do the same with most everything that has a break in period, like capacitors, or even cables, you will get the same results.