My vet agrees that the time can be extended significantly for indoor-only
cats, especially those that have previously had a series of rabies shots.
However, he still stresses distemper shots because it is airborne. Do you
agree?

In 2000 the AAFP (American Association of Feline Practitioners) recommended
that "following the initial series of vaccinations and revaccination 1 year
later, cats should be vaccinated no more frequently than once every 3
years".
2 years ago I spoke with the AAFP representative at a meeting and he didn't
recommend vaccinating strict indoor only cats (don't even go out on the
porch) due to VASTS. I haven't had any of my cats vaccinated since then.
But, that's just what I decided to do, and it doesn't mean you shouldn't
follow your or your own vet's instincts either.