High Up or the Low Down with Tube Burn In

Is there a typical response to tube burn in, that is, theoretically, what happens - bass opens, highs "smooth," etc?

I'm relatively new at tube rolling. I recently added the Wyred 4 Sound SX-500 monoblocks to the rig. I had electroharmonix 12AX7's with which I replaced the stock tubes in my Jolida JD-100. With the new amps - even after a good bit of break in - the detail was fantastic, good soundstage but the highs a tad irritating and the bass lacking.

I just dropped in some new-issue Mullards and - carumba! - the bass really amped up but the highs and detail are now (too much?) attentuated. Could the highs open up with breakin? I think I've read that typically the highs mellow out a bit.

I'm digging these amps; I think they reflect pretty much what comes before them in the chain.

Well, I guess this is the beginning of the tube-rolling journey. There are a few more reasonably-priced brands out there before I'll consider paying big bucks for NOS. I'd rather not go there if I don't have to.

Understood it may be nigh impossible to get "smooth" and "detailed" with good low end in the same tube but these two examples to date sound like they are at opposite ends of the extremes. I'll look for some Buddhist "Middle Way" tubes.