How often should I check on Foxy?

I'm going to assume you're playing FNAF 1. In that case, you need to check on him really often if you're playing 4-20 mode, but not keep the monitor up for that long. That's what the wiki means. This might come as a surprise, but you don't need to check on foxy's camera in particular, you just need to check a camera. So you can look at cam 2, and it will count as checking on him. That allows you to cam stall Freddy on cam 2.