Feline annual flu-booster vac - necessary?

Hi.

Our vet seems to have boosted the price of the annual flu-enteritus
feline vaccination boosters this year by quite a large amount.
Unfortunately, there are only two vets within a 30-mile radius. But
while I am angry that he seems to be making a packet out of the annual
jabs another question has popped into my head. Are these jabs really
necessary at all?

A friend says she read that after the initial jab and maybe one booster
no more are necessary at all.

A neighbour has an old cat whom she has never had vaccinated at all and
the cat is strong and healthy. The neighbour is very much in natural
solutions, natural immunity, etc.

Another friend says that even after flu jabs one of his cats got the flu
two months later and almost died - had to spend a week at the vet's.

The other thing is we live right out in the country. People round here
don't get colds and rarely the flu because of all the fresh air and lack
of people. Maybe the same thing goes for cats?

Added to that my two are strong healthy creatures that spend five hours
each day outside climbing trees, exploring woods, racing across fields
etc.

What do people think? I would be glad to hear many people's advice.

Thanks.

Annual vaccines are no longer needed or recommended by veterinary
teaching hospitals. Every 3 years provides more than enough immunity
for adult cats. Some newer studies show that once a kitten finishes
its vaccine series, and is boostered 1 year later, the immunity lasts
for life.
I personally follow this for my own cats, as do many of my co-workers.
We follow the every 3 year protocol for our clients due to the legality
(as in studies are not complete for the lifetime immunity as of yet).
(vet tech)