How often should fuel injectors been cleaned?

replace every 100000 miles, a gasoline based cleaner available from any motor factor should clean the entire gas system on your automobile. I use Shell V-Power in the UK, this cleans the system and gives better MPG! but costs slightly more than ordinary gas

overkill???

Overkill! Use "top tier" gasoline and maybe twice a year use a bottle of Techron fuel system cleaner and you are good to go.

Bob and the others are completely correct. Just using a Tier 1 fuel in itself prevents many issues. Techron fuel cleaner is a good choice.