Do ninjas have extended lifespans? Most ninjas probably don't live very long by the nature of their work. They die on missions, in wars, in raids, while being ambushed by other ninjas, during testing, etc. 

However, the handful of ninjas we have seen (e.g. The Third Hokage, as well as Tsunade and Jiraiya) who've lived past the usual lifespan seem to be of very advanced age.

Do ninjas have a longer natural lifespan that is simply cut short by the nature of their work?
Not really, no.

The oldest (probably) Shinobi alive was Madara Uchiha, and even that because he awakened the Rinnegan, summoned the Gedo Mazo, and leeched on it for life-force.

Without it, he would probably have died at 80-90, which is a reasonable lifespan.