That sounds a lot like, "If it ain't broke . . . " advice.
If you are getting a diagnostic message to replace the battery, then do it. Remember to power off first. The battery is a very tight fit; so, be careful and be gentle. If you have a clean power on self test, then there is no need to replace the battery.
The scope will operate with a dead battery but the last settings prior to power off will be lost. If you ran the EA (enchanted accuracy) to trim the offsets, that will be lost as well with a dead battery. The battery allows you to resume operation between power cycles with no fuss.
Factory cal constants are stored in EEPROM. They do not depend upon the battery.
Check the service documentation if you are nervous.
The memory expansion board (non-A model upgrade and all A models) also has a battery that saves the 10 setups and the two waveforms. Yes! It can store and display waveforms from memory, but that's another topic.
I have been amazed at the life of the battery. Mine lasted more than 30 years! That's a lot of margin over the 5 year guaranteed life.
And a guaranteed 10 year shelf life