It's a good idea to re-bias when changing tubes if you want the best results with your amp.
PRS amps have external bias points, so that makes things pretty easy. No need to remove the chassis or hunt underneath for bias points.
Fenders require a bit of fussing to get to the bias points, and you have to know what you're doing because voltages inside the chassis can be dangerous.
Mesas aren't really self-biasing. The bias is hard-wired to a given setting. Then Mesa sells tubes that are matched to work with that setting as measured by their test equipment.
There are mods for Mesa amps that allow bias adjustment; a tech I used once did that to my old Tremoverb (without asking!), and basically messed up the amp as far as I was concerned. It was better sounding before the mod.