I think it depends how you want to tell people.
If someone buys something from you, and you say include an offer code within their parcel for next time then fine.
I wouldn’t recommend sending emails to people who have ordered from you before though. For most people that’s a total turn off as they haven’t actually given you permission to use their email address for marketing, and most people will just delete without reading the content because it’s annoyed them. (I do this.)
I don’t do anything like this personally, I’m one person & making my artwork takes a fair length of time & I’m unable to constantly create- so I maybe maybe one type of print a month. So I can’t afford to run offers. I did experiment once with running a 20% off offer on here & Etsy at the same time. I promoted it on Twitter, Facebook & Instagram and while I sold a couple, it was of my cheaper work anyway & I’ve sold more in weeks with no offers at all- so for what I sell, It doesn’t seem to make a difference. I often wonder why small sellers run discounts- is it because they can’t sell their work at the current prices?- that’s why I experimented, to test the water to see if my prices were too high. So maybe that’s what people think- which may have a negative effect? After all, big shops simply have sales to get rid of stock they don’t want any more.
I would always say experiment! No harm. It can be interesting as well to see what works & what doesn’t.