iPhone OS 2 (the version before it was renamed iOS) was announced on March 6, 2008, and released on July 11, 2008. It was actively updated until its final version 2.2.1, released on January 27, 2009. So, the active update support span for iPhone OS 2 was about six and a half months after initial release. If the question is about how long iOS 2 lasted in terms of usage or support, typical Apple support for iPhones tends to be between six and eight years, but iPhone OS 2 itself was superseded quickly by later major iOS versions starting with iOS 3 in 2009.
In summary:
- iPhone OS 2 initial release: July 11, 2008
- Final update (2.2.1): January 27, 2009
- Duration of active updates: ~6.5 months
- Usual Apple iPhone support lifespan for devices is 6-8 years, but the OS versions update annually.
