If I am using the battery in cyclic application do I have to de-rate the battery float life according to the temperature where the system is going to be deployed?
The float life is the upper limit to the battery life. Even if you never use the battery, or you use it very lightly, HOMER assumes it will require replacement when it reaches the float life.
Ideally you would consider the temperature when specifying the float life. I can't tell you how the float life varies with temperature, except to say that in general the float life decreases with increasing temperatures because of the accelerated rate of corrosion at higher temperatures.