In Nov.2014, we were visiting one of our customer in Europe ,we saw our garage door motor "Bearsafe" (PAX-II) was testing with the door ,and it is continually working (keep up and down ) ,the number of testing time was 89,773 times and its still working . So you can calculate like this :
If you open your garage door 10 times / Day ,means 89773/ (10*365)= 24.59, so means the life of the motor will be 24 year !!!