I have two cats, they see the vet every year.
The rescue I volunteer for asks for a vet reference on adoption applications. We consider a “good” vet reference someone who had all their pets spayed/neutered, had all pets up to date on shots and who took their animals in for regular veterinary check-ups. We do not consider “proper veterinary care” taking your animal in to the vet just when the animal was sick or injured.
the superkittehs go in annually whether they think they need to or not.
being indoor-only cats they don’t get every shot every time, but for my own peace of mind i have them gone over: hair skin eyes teeth, etc.
i do it for me with a physical (and other fun things like mammograms and p&p exams) every year. why not take care of my favorite furballs the same way?
My vet was always concerned about feline leukemia so I always made sure that one was up to date. And yes, the teeth, the teeth can get nasty.
I’m not sure about San Diego specifically, but according to this slide show from the American Heartworm Society, there is at least low-level to medium-level of heartworm cases in most of California. Certainly less of a risk there than in Louisiana or Florida, but it is not zero. Also, indoor-only is not a guarantee againt mosquitoes. I’ve killed plenty of them inside my house (granted, I also do not live in California). 
Lastly, many heartworm medications also:
BTW, if you cat comes up with tapeworms, guess what? The kitten got into contact with a flea, as those are the intermediate hosts for the common tapeworms in cats.
This thread made me realize my cats are seeing their vet more often than I see my doctor! I just scheduled a physical (for me).
I’ve been lax about taking my cats in for checkups/boosters, and after my current cat fell ill last year I resolved to take her in for her yearly checkup.
Naturally, the vet sent me a notice for a 6-month checkup. Some kind of intranasal injection, but I don’t have the specifics in front of me right now. Is that really necessary? The cat will be just about rehabilitated from the trauma of last year’s visit by the time the next one rolls around.
My cats get FVRC intranasal drops, which are for “upper respiratory disease complex.” It’s very common in crowded conditions such as animal shelters; I have two rescue cats who had it at their shelter, and it was cleared up before we were allowed to take them home. Bosstone: since a checkup is overdue, I suggest you go ahead and take your cat in for exam, vaccinations, etc., and ask the vet about anything you don’t understand. If your vet doesn’t want to take the time to explain his/her procedures, get another vet. For instance, why an exam every six months, and what are the various treatments for. My cats’ exams are once a year unless there’s a problem. Also, my vet spends time with me going over the treatments, tests, and results and what they mean, and explains the financial implications of various treatments and tests. You’re paying for the vet’s services, and you have a right to ask for information or to seek another vet or a second opinion. As I said before, prevention is easier and cheaper than tests and treatments which, in the end, may come too late to save your kitty.
P.S. for Bosstone: The vet can give you a tranquilizer for your cat to make the process easier. I have a male tabby who went berserk and shrieked like a banshee in the vet’s exam room. The vet couldn’t conduct any kind of exam. She had given us a tranquilizer but it wasn’t strong enough, so next time, the vet put the cat, in the carrier, into an enclosure (a big bag I think) and put some kind of sleeping gas in it to knock him out. So again, talk to your vet about options for this situation. Neither you nor your cat needs to be traumatized by the experience. Good luck.