How frequently do you guys change your hydro fluid? My instinct tells me to change all the fluids everyspring but the mower only has 18 hours on it and it seems like a ***** of a job. To all the Ztwo and Cub Cadet owners how difficult is it to do? I have the '07 Ztwo with the smaller resevior and the filter in the tank. I was looking at it this morning and really didn't see and easy way to do it.