Nope. Not anywhere worth it, unless you have a distemper outbreak in your area - even then, titer first.
Absolutely. IF you're in Iowa there's an excellent chance your dog has been exposed repeatedly through the years. In the absence of vaccinations those exposures 're-immunize' & simply further reduce the need for annual distemper shots. My previous vet (now retired*sob*) advised against doing em after the initial 2 or 3 almost 20 yrs ago. I never get them even on my seniors but
I'd consult the vet if my dogs had chronic health problems or wonky immune systems.