Heartworm Med. and Yearly Shots...

Blaze is not on any heartworm medicine and I was wondering if this was ok? My friend who is a vet tech has a cat who is not on any medicine and stays inside all the time like Blaze and she says its fine but I just want to be sure. Reggie(friends cat) also doesnt get his shots every year he gets them every two years (except for his rabis of course) so i was just wondering if this was ok to?
My friend is very set in her ways and swears up and down it fine if they are not on Heartworm meds. because they never go outside and heartworms isnt a big problem in cats. I know if i call the vet they will insist on getting yearly shots and getting Heartworm treatment because it is a way for them to make money. I was just wondering what the other cat owners out there did...

I never even knew you were supposed to put a cat on heartworm medication. Is this only if they've had it or is it supposed to be preventitive?

No this is not something that you only use if they have had them. If your animals goes outside at all (even for a few minutes) it needs to be protected. Or that is the way that I understand it. Now if your cat does not go outside ever than I am not sure. I have Meater and Chino on it all year. :D