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.
you have discovered that each type of tube varies in sound by brand, year of manufacture etc...I've found a new in box tube seems to burn in within 5 or 6 hours...you know what you'll be getting after that....so best thing to do is read this forum postings or especially AudioAsylum on different tube types and their sounds, brand distinctions etc.
have fun
I agree with Larry it doesn't take long to get the real sound of a new tube..Pretty much the next day...I really like the Ei cryo 12ax7 very much..Also have heard many like the Chinese Shaugang ( spelling ? )..12ax7 also...
EI is on the shortlist as a practical alternative. I've ordered a couple of Tungsram in the meanwhile.
I must say I'm impressed with the "weight" of the Mullards.
Not sure, but I think I may have read that the Mullard re-issues are not really anything like NOS British Mullards.
Cjack : The Tungsrams 12ax7 have great bass weight but I actually prefer the Cryo'd EI 12ax7 ( Thor t1000 mk2 ) I got from Ken at Tubeman.com...I am on my second pair and Got many hours on the first pair and just fired up the second pair..Plenty of detial without any edge....I know many love Mullards but they were just too darn warm for me....
Wouldn't be surpised if Mullard re-issues are not really anything like NOS British Mullards.
To me, at his point, it's just a name with a price. Pretty impossible to audition this stuff, so ya pays ya money and takes ya chances.
By no means do I think the new Mullards are "it."
Recommendations can be scrutinized for some trends but still, hearing is the thing.
Those EI's might be the ticket... Whatever is "it," I hope I find "it" soon.
I try the RAM 12aT7 low noise (super) IN MY vtl 150 AND Put my telefunken on the shelf. I heard the differnce as soon as I installed them!