2-3 times a week, every so often only once a week. I'd love to do more but me being on my own most of the time, it's hard when LO hates water. I don't do it at bedtime for the same reason and also because there's so much going on in the evening already (bottle, his dinner, preparing and hopefully eating my own dinner, wipe down, and bedtime bottle).
I also read of someone on here who had to give her LO a bath in the middle of the day once and the baby got confused and thought it was already bedtime, so I avoided making it a bedtime routine. Usually I do it some time in the afternoon.