Replacement same model tweeters like a major component upgrade

Hi all. So I blew a tweeter last week on my Martin Logan dipoles. I called ML and got a pair of replacement tweeters. I removed the dead tweeter and installed a same exact replacement model from ML. Hooked up speaker and it sounded more extended and fuller and more detailed in the FR above 2500 crossover than the other. This was immediately obvious and was confirmed by playing mono tracks on Qobuz. So since I had ordered two, I changed out the other. Bam!!! Brand new speakers!  One cannot overstate enough the importance of the tweeter in the resultant sound quality one gets. The pair of speakers now sounds better and requires less EQ (I use high end pro balanced analog EQ for years). The best upgrade I’ve done so far. By far. And I never would have thought to do this were it not for that fateful day last week. Amazing!  Would have expected a rough edgy sound worse situation initially until broken in. But quite the opposite. 
so my questions are 1. Does a tweeter not need break in?  This is a “magnetically driven planar tweeter. The latter, which MartinLogan calls an ATF Transducer, measures 1.5" by 2.25" and consists of a lightweight film of polyethylene naphthalate film with an etched aluminum voice-coil, which is sandwiched between sets of neodymium-iron-boron magnets in a rigid steel housing.”

and 2.  Do tweeters degrade over the years, such that they lose both extension as well as resolution?  It’s astounding what a simple same model replacement has done. 
And finally, 3. Do we sometimes “upgrade” speakers when we could have accomplished the same thing simply installing new drivers at much less cost?

Thanks all for your thoughts!