Hello amino,
the it depends on model and ambient temperature.
The manual say for a 400/600 series model typical 64 h at 25 degrees celsius, and typical 24h at 40 degrees celsius.
For a 500/700 model it's more complicated. time value depends on Temperature and age. For a new 5/7xx easy at 25 degrees, it approx. 190 h. For same models, but after 11 years of service , it decreases to 140 h at 25 degrees and 20 h at 55 degrees ambient.
etc.
So, to give a precise answer to your question, it would be helpful to to know more about the specific model you use, the ambient conditions, etc.
BTW: RTFM is here a good idea too (Read The Fine Manual) :-))
hth,
Andreas