Many LND releases contain security fixes, so you should be upgrading at least a few times a year.

The default embedded db (bbolt) can only be compacted while offline, and the longer you go between compactions the longer it takes. This may not be significant for a personal node, but for a busy production node it’s likely to cause peers to temporarily disable their channels (if the outage lasts >20 minutes). Without compacting, your disk usage will grow and performance will suffer.

Restarts can be relatively quick (by bitcoin standards, not by enterprise standards) by issuing an external db.

The biggest risk to an RPi besides power is SD corruption. Using an onboard UPS (like PiJuice) can help, because SD corruption is more likely when power is flaky, but ultimately you’re just delaying the inevitable.