Just keep checking. When I bought mine a while back, I found that they were having sales early in the morning - I'd get in to work at 6AM and they'd be on sale, but by 7AM they were back to normal price. This happened several days in a row then stopped.

I don't know if they have a regular sale pattern though.

I have a folder full of links that I hit first thing every morning, and I just middle-click that so a couple dozen tabs open up. If there's a contest I want to enter every day, or something I'm watching for a sale on, I just add it to that group. OK, it's mostly web comics, but there are a few other things in there.