USB enclosures usually aren’t built to be left on 24/7. They might do it for a few months, but I’ve seen a lot fail around a year or two.
If it’s that your just going to plug it in once a month for updates then let it set offline - what you want to do will work just fine. But then you may as well just plug it directly into your computers.
If you shuck the drive they seem to do better - dunno if it’s the crap electronics they have inside or the case itself
If it’s long term - just invest in the NAS, you don’t need 18 bays and you certainly won’t regret it. Lazygamer’s Pi idea is a good option too.