I do not like the idea of using IPs for that either, but since it's only for the timing instead of locking people out of the service, it's less of a concern.

And as db0 said IPs are far from optimal but they're the best thing that "we" [actually the devs] have available. If you have some alternative way to discourage simultaneous multi-accounting, by all means, suggest it here.

Same with people who use VPN per default.

That's the closest thing we have though. The alternative is just people using alts, and at that point might as well not have limits. There can be ways to add exceptions if needed.