Coys68 Working in IT I am also quite firmly in the 'if it isn't broken...' camp, the number of updates that cause problems in the world is countless.
However I usually consider 3 things. (1) Yes security improvements are often, but not always, part of updates. So there is a (sometimes exponential as more exploits are discovered and have time to be exploited) increasing risk over time when not updating. (2) That lab / beta / pre testing often might not cover the direct update from very old versions directly to new versions - so you may be deliberately trying to make yourself a test case (3) The potential benefits of new features and the reliance and interoperability of other devices that may be on newer firmware and again not well tested against very old versions (eg the case of updating your AIO to latest to improve BMS abilities, but never updating the AIO).
Here there may be safety implications, the prtoection of incoming fuses, other downstream devices to consider too, with this type of equipment specifically.
Never an easy choice.