I know that eventually you will be asked to measure the current through the tube eventually, so if you know how... and what aschematic shows and what is true may be quite different. The bias voltages are relatively meaningless without knowing the current, plate voltages, etc, so we'd just be guessing. And given the (in)consistency of current production tubes... Don't worry about what others say is too hot or too cold. If the amp works and sounds good (or better) AND doesn't self-destruct, it's fine.
That said, I'm assuming those are Sovtek 5881WXTs in the amp. If you replace them with the exact same kind (Sovtek 5881WXT), there's a chance you'll never have to adjust the bias again. Those things are damn-near close to "the indestructible tube" as we ever got. Don't confuse them with
NOS 5881s or the new Tung-Sol reissues or the 5881/6L6WXT. Check the innards of the tubes, and if they match, you're set.
As far as EL34s go, I'd take every precaution I could before plugging THOSE in... which to me would be a bias pot AND making sure my power transformer won't burn up from too much heater current draw... also may require some rewiring of the tube socket, grid and screen resistor values, etc.