You’d think I’d know by now…

I have the opposite problem with pasta. It never looks enough dry, so I add a couple more handfuls, then there's usually enough for two-and-a-half more portions (the excess is never a round number, sigh...).

More spuds is the answer.

I always aim for leftover mash because of my addiction (fried potato cakes with a fried egg on top)

Too much mash never wasted.
Dont really like it out of freezer straight as mash
Try letting the mash go cold in a square dish about one inch thick cut into squares, brush on a little butter and heat in air fryer till it goes brown

I’m the opposite, often do too many!

But I just freeze the spare, never wasted.

Same here..I usually end up adding sweet potatoes to the mash to eke it out. I forget that people have different potion sizes too.😃