In general it’s advised to always update your device’s firmware to the latest available version as new firmware usually brings either new features or some security fixes or improvements.
Only firmware versions featuring major security fixes are mandatory, others are voluntary so it’s really up to you.
We understand that BTC and crypto is about hodl and big number of users may not use their Trezor on regular basis but rather use it from time to time to check or spend their precious sats. In general this shouldn’ŧ be a problem but from time to time a firmware update is necessary.
Some coins do undergo updates or upgrades to its code and functionality and some of these changes are not backwards compatible, hence you may need update the firmware in order to access/send/receive given coin (please, note that this is not matter of Trezor Wallet but the coin itself, we need to update the code so the coin can be used with Trezor).