Ugh, I have an egg skelter too... and I HATE it!
The eggs up top don't roll down as an egg is removed and then if you give them a little push they roll down but are pretty scrambled, We can't use those rollers without popping the yolk. And my eggs aren't all the same size. Some wanna roll end over end instead of on the side. I shouldn't have to assist every egg to the bottom. And yes, I read reviews and bought one that was mostly good. Good idea, bad reality for me.
What I wonder.. is with the float test, what are you really checking besides the size of the air pocket in the egg... which does NOT equal rotten. Not arguing here, just trying to learn also.
Seriously, I got overwhelmed with eggs this year when my flock reached at least 30 layers for my family of 3.

Anyways, I had a lot of eggs that were 2-3 even 4 months old unwashed and unrefrigerated. My room temp is about 60. The yolk was stuck to the inside shell on some of them (what you try to avoid during hatching). A little runnier. And I'm sure the nutrient quality was diminished. But VERY few were actually rotten and those were ones that got smashed or cracked.
Glad that egg skelter is working out for you! I won't even give mine away and been considering throwing it in the trash.