You ever notice how the gear you trust the most is always the stuff that's been crammed in a bag since the last job... yeah, that's how it works for me too. I had a backup mask sit in my truck for six months, and the strap turned to crust, fell apart the second I needed it. We're all just hoarding junk until the worst possible moment, I swear. At least you got a spare reg in the truck, I've had to borrow a buddy's O2 bottle on a dive once because my backup everything was garbage. Now I check my spares every month, like a weird ritual, just to feel less dumb about it.

It's just concrete" while you're bull floating in 95 degree heat? That's like watching a chef after a 14 hour shift and saying it's just food. They have zero clue that the finish is what stops water from getting in and blowing the surface off in a few winters. I'd have been tempted to hand him the trowel and say go for it, see how easy it is.