You should always back up every key. So, in a 2 of 2 losing 2 keys and 2 backups is unlikely. 3 of 3 is unwieldy in general use but also with setups using CKBunker, or decay threshold N of N wallet setups are not as dangerous anymore.
Discussion
Decaying threshold reduces the risk.
If you’ve got that setup it’s not as bad but you’re still locked out of your own funds for some period if you lose a key. That inherits the risk profile of time locks where if you feel like your keys are compromised or at imminent risk then you can’t move funds to a new setup in time. It really depends on your threat model.
If you’re backing up 3 sets of keys then you’ve got at least 6 to keep up with, which makes recovery easier, but for each one you have to maintain security. It creates more opportunities to leak your keys.