Vaccinations every 3 years?

Does anyone get their cats 3-year vaccinations? What do you think of this?

I had been getting the 3-year rabies vaccinations for my cats but I recently saw that my vet also offers a 3-year combo vaccination (FVRCP).
I would like to do this so they don't get over-vaccinated but was wondering if anyone else has used these. I know with the rabies the 3-year vaccine is often identical to the 1-year, it is just labelled for 3 years but I don't know if it is the same with the combo.

If I decided to go that route, I'm going to have to check if the animal blood donor program I enrolled Spot and Blaze in accepts the 3-year vaccinations... I also wanted to enroll two of my other cats in the program assuming they reach the minimum weight requirement of 10 pounds (they are just under it) so if they don't accept it I will have to decide whether to enroll them and get vacc every year or not.

I do not do 3 year rabies shots because they have stuff added to them.
I do the Purvax 1 year shots.

I only plan to vaccinate my cats and dog every three years. If I could, I would also give them the separate vaccines 2 weeks apart instead of the combo FVCRP. My cats don't go outside so to me there's no big incentive for me to poison my babies.