Hey dude, I have a tweaker 30 so I can comment! I've never had to change the tubes in mine since I've only had it since May and I've never read much about switching the tubes on them either. But it's a great sounding amp! There really are a ton of sounds in it. I end up moving knobs and flippin switches like after every other practice and I'm like "Yeah this sounds awesome! I'm finally gonna keep this setting!"
It's got pretty good headroom I guess (first tube amp) since it sounds like you want it pretty clean. I can turn the gain up a bit over halfway with the hot switch set to clean and you have a little bit of headroom on the hot side of it too.
Sometimes I wish I would have gone for a tweaker 15 instead since I don't always know what I want to do with the second channel and MOST of the time, I don't have to turn it up past 12-1:30 on the master vol. But FYI guitar>fuzz>amp with some od/higher gain = nasty nasty fuzz tone. I have this awful trashy harsh octave fuzz right now that I kinda hate but it sounds like a fuken beastly big muff when I max it out and run it into the amp od.
I can try to answer any other q's ya might have since I'm just talking to be talking right now.
Also, ILFer julius_deane pointed me to the Egnater renegades (which you might also want to check out, they have reverb, different tubes, different toanz) and Egnaters in general and I ended up choosing a tweaker over that, and some oranges, fenders, vox, and some others that the dude at GC let me try out all side by side. And I've also read that jet city's dont have a ton of headroom and that seems pretty important to you. I say go the extra mile for a tweaker! And they just look so kewl

But also rememba, I have the 30 which (correct me if i'm wrong) I think more watts = more headroom (kinda) the 15 = less watts so yeah.