I've had mine down for a couple months now. I did two coats, and clear on top. Waited 1 day between each coat, and 7 days to park on it. My slab is 56 years old, and I didn't even do a real ******** cleaning. Just vacuumed and acid etched, the floor still looked terrible before I layed the epoxy on.
It still looks like the day I rolled it on, but I'm only a few months in. I've had 2 cars parked on it every day, dropped tools and dragged furniture across it and it seems plenty tough. I would reccomend 2 coats though, the first coat was pretty much all eaten up by the concrete, and really acted like a primer. I'm also happy I did the clear, another layer of protection and added a nice shine. Mixing was easy, 1 to 1, and it didn't smell as bad as expected.
I would reccomend it thus far. Ask me again in a year and I hope to give the same answer