I have planed down a herd of "old" wood over the years. I usually wait until the planer is getting a little dull to do much of of it. I also usually set up outside in a breeze where I don't have to worry about what it might have been finished with (like lead based paint). I have yet to completely ruin a set of planer blades. A tiny nick or two yes. Most of the time just shifting the blades end wise so that none of the nicks line up takes care of any ridges until I get done with the used stuff. I sharpen my own blades and keep several sets. The Foley/Belsaw has fairly heavy blades and I have ground some sets several times.
I keep saying that I am "old school" and that applies to planers too. I subscribe to the old statement that "the planer is a dimensioning tool, not a finishing tool". I do not shoot for a glass smooth surface on every piece of planed lumber. As long as it leaves a surface that can be very quickly sanded to a ready to finish surface I just keep planing. Even if it comes out like glass I am still going to sand it so why sweat a few teeny little ridges on the surface.
I did not equip with Shopsmiths in spite of the setups but because of them.
1 1988 - Mark V 510 (bought new), 4 Poly vee 1 1/8th HP Mark V's, Mark VII, 1 Mark V Mini, 1 Frankensmith, 1 10-ER, 1 Mark V Push-me-Pull-me Drillpress, SS bandsaw, belt sander, jointer, jigsaw, shaper attach, mortising attach, TS-3650 Rigid tablesaw, RAS, 6" long bed jointer, Foley/Belsaw Planer/molder/ripsaw, 1" sander, oscillating spindle/belt sander, Scroll saw, Woodmizer sawmill