About 40, of which I only use a few. It actually got me started on a project: how can I minimize the cost of keeping all of those domains. After a lot of tinkering I could cut costs with a healthy amount, not sure if it was worth all the time I put into it though, haha ;)

Maybe it will help someone out: https://www.dot.bs/registrar-combinations -> copy-paste a list of your domains, and it will find the cheapest combination of registrars for you