Not really. Pretty much the only times I've seen users exceed the rate limits were when a) Reviewable had a bug, b) some other app they were using had a bug (l

Not really. Pretty much the only times I've seen users exceed the rate limits were when a) Reviewable had a bug, b) some other app they were using had a bug (limits are per-user), or c) when they were backfilling the reviews on initial signup and a lot of PRs were open. You do have to be careful not to exceed the burst quotas, though, which are largely undocumented for "security" reasons. If you get a 403, make sure to pay attention to the Retry-After header (my open-source Hubkit library will do that for you automatically, and a bunch more).