Yes and: Maintain your balance. Get tested (assessed). Do the exercises. (For anyone who hasn't heard.)

My mom and her bf were hard core. Swimming, biking, running, the works.

They served as one of the hosts for BBC's program Are You Fitter Than a Pensioner? [2010] https://www.bbc.co.uk/programmes/b00tyr5n My mom was 70 at the time. Spoiler: The seniors smoked the youths.

Alas, as with so many: falls -> injury -> idleness -> decline.

Some balance stuff can't be helped. Mom's bf got spells of vertigo; apparently the little balancing sensor bone inside the ear gets loose with age.

Your mom's boyfriend probably already knows this, but just in case: I once suffered from loose crystals in my inner ear (probably due to stress and burnout) and had such bad vertigo that I thought I was going to die. There are exercises that move the crystals back to where they belong, where they get absorbed and metabolized again. It's called Epley maneuver, and while it can be extremely uncomfortable and should preferably be done under supervision (some people throw up when doing it) it solves the issue quickly and pretty much permanently.

I've heard of people who lived months or years even before figuring this out.

There's some hoping that some maladies of aging such as vertigo are more treatable in the coming decades, for those fortunate to be alive by then.