I use it every few years very rarely if ever, my 300E never saw injector cleaner in 155K ans started and ra perfectly. When I have used it I used Chevron Techron, stay away from the $0.89 a bottle stuff.
If you are typical, you shouldn't need to use any FI cleaner in your car. This assumes that you fill your car with fresh gas from a major supplier and do not store it for long periods of time. AFAIK, all major gas suppliers blend small amounts of detergents (cleaners) into their gas. If the gas is fresh (not allowed to "gum" or lacquer through aging) and your fuel filter is changed regularly, you shouldn't have issues with injector cloging. I would, however, use a sing tank treatment annually as a preventative since it is reasonably cheap insurance against elements you do not control.
FYI... Please beaware that if your dealer sells you their "Injector Cleaning" (typically for $125 - $180) you need to investigate very carefully and ask specific questions on what thier process includes and what product(s) they use. To my knowledge, all they do is to put a quality injector cleaner product into your tank for you (thier cost is $5). My wife seems to get talked into this everytime.