Yes leave plugged in and switched on at the wall socket.
Don't run the ups till it shuts down.
Don't leave it uncharged for a long time.
Don't put in a cupboard/enclosed space where it will get hot.
Use it for what it was made for to safely save your work and shutdown your PC.
It's just too much effort trying to save Lead Acid batteries you need constant monitoring of voltages and can't discharge them more than 50% even that is too much
I would just replace them with Lithium batteries when they are dead. The Geewiz one's work perfectly in UPS's