I've not really cared much for sales when it comes to pc parts, I usually find the cheapest seller between the different amazon sites(though it's recommend to buy from Amazon instead of a marketplace user) and some known local sellers.
I then calculate which parts are the cheapest based on shipping as well, also consider the shipping time and then order them all at once.
You could wait for sales if you're patient but you might find yourself waiting for long time.
Also it depends if I'm just looking to buy "at some point" a new monitor for instance then yea I could wait, it all depends on the situation.