If I have seen your ad multiple times and not taken action, it is time to show me another ad, or fix your checkout flow.
In general though ad tech is so primitive it is embarrassing. I am an Atheist (and have plugged this into Facebook), then they try to sell me ads for magic crystals. An Atheist would by definition not be interested in that.
Then they tried to sell me gas, from a gas company 300 kilometers away. Then, after I had filled out the section about my education, showed me ads for the exact degree from the exact university I had told them I got the degree from.
I am a single man, so Facebook decided I wanted to be showed crappy for pay dating sites[0]. The only dating sites where I would have a chance are the big sites and you don't get big in the dating space by charging.
I searched for and got an apartment, then google showed me six months worth of ads for a crappy apartment finder site.
Google any electronics and you get ads for it weeks after you buy it.
Instead of figuring out what people by after and then show ads for that -- I might still be interested in buying custom fitted curtains, for example.
There must be products and services out there that would actually benefit me, and I certainly have the capacity to purchase them, but somehow those never show up.
[0]: you should never use them http://static.izs.me/why-you-should-never-pay-for-online-dat...