Do titles on sale vary as time passes?

For those who have been living under a rock for the past few days haven't been informed, the 2016 Steam Summer Sale started yesterday. There are a few games that I'm really looking at buying, but I don't have the money in my Steam account and I don't know if I'll be able to grab another card until Monday (and no, I do not have another form of payment). Part of me is worried that it will no longer be on sale by that time. Does Valve periodically change which games are on sale and which aren't or are all of the games that are on sale going to stay that way throughout the sale?