My thought is yes. Our first kitty, Smokey, died at just under two years old having been born with feline leukemia. We had never heard of feline leukemia until Smokey. It was a heart-wrenching thing to watch.
We now have Hershey and Oreo, ages 10 and 5. They both had their initial shots and boosters. Apparently, in 2010, at an appointment I don't even seem to remember - so not sure which of us took them in - we opted out of further boosters. Hindsight can see why we made that decision - they're our only cats - we don't plan for more - they are strictly indoor and are never around other cats. Makes sense - yes?
Hershey was diagnosed with FD Nov, 2011, again - never knew cats could get it until he was diagnosed. They had their annual checks that day and were brought up to date on their shots. I didn't ask "what shots" and nobody refreshed my mind that we had declined boosters. March, 2012 - We went out of town and left Hershey with a sitter. Have since learned that a kitten in the house had tested positive for feline leukemia. We have to wait until July (incubation period 16 wks) to have both of our cats tested. Praying for negative results, then you'd better believe we'll be doing the shots/boosters, again. AND - when they say my guys are 'up-to-date' I'll be asking more specifics!
Just my two cents, but the <$30 booster is well worth not having to agonize these 16 weeks over whether or not they're positive and having to live with the consequences if they're now both positive.
Libby (and Hershey, too!)