Reed Life Expectancy

The biggest factor that affects the life expectancy of the reed on a thatched roof is the pitch of roof that the thatch will be applied to.
For instance, the steeper the pitch the faster water will be dispersed, therefore the shallower the pitch the longer it will take for water to disperse, hence shorter life expectancy.

Other factors may also include the quality of the material used, the skill of the thatcher and also the location.