I've got accounts on a lot of sites across the network. Some I use daily, others are more ad-hoc.
Every time I visit a site I haven't seen in a while, I get
Welcome back! If you found this question useful,
don't forget to vote both the question and the answers up.
It's okay. You can relax, I haven't forgotten how the sites work, and I really don't need you to keep telling me for no reason.
I'm not sure of the original rationale, so there may be a good reason for it. If so, tracking visit date across the network would cut down the noise to near-zero.
Alternatively, perhaps anyone with a rep > 1k on any site gets a pass?