Because of this, it's also customary to use a LIMIT just in case.

For something like this, LIMIT 3 if you assume the query is correct (e.g. in production), or LIMIT 4 if you're running it manually -- so that if it reports 4 rows changed instead of 3, you know you messed up somewhere, but at least you only have up to 4 rows to fix by hand, rather than an entire table.