Base stacks mage using galvanized are still in use throughout much of the maple world. I'm not sure how long 20 ga will hold up, I think most galv. base stacks are a little heavier, but you certainly will get a few years out of it. As that needs replacing, consider a SS base stack, in normal use it should last several time longer than the galv. one.
Dave Klish, I recently bought a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.