Now that you've had a pool and lived with it for a while, what things do you wish you'd known before you started?

For me, the big ones are:

1) Electrical consumption. I had no idea that the pumps needed to run so much and used so much electricity. I'm paying an extra $75/month for electric just for my pool.

2) Sand. My coping is sandstone. My Rocks are sandy. I almost always have sand in my pool. I've sealed the coping and that helps. I've also been told that the sanding slows down over time. Still, if I had to do it again, I would have picked a different coping.