I have been doing this for 3 years now and none of my stuff is wore out YET. Some is new this year. I am starting to do more large jobs (25 and 32 hours per week) and need to be closer with my overhead projections. Been searching and think that the 100 hour per HP (mowers) seems like a common answer but is that real and what about hand held stuff like trimmers. all my 3 year old stuff is 2 cyc. and the newer is 4 mix by Stihl. All maintenance is by the book, 01 belt 48" Exmark 15hp Kaw (2) 03 belt 48" Exmark 15hp Kaw 04 hydro 48"TThp 17hp Kaw 04 hydro Proline 36" 15 kolher 04 Toro 27 hp 60" 500 Kolher (2) Plugger 800 Honda 03 (4) Echo 230's and 260's trimmers and edgers 01 (3) Stihl 4 mix 04 I thank you for any help you may have to offer. Now if anybody can tell how many hours a 40something body has left that would be super.