The thing is your servicing a sealed unit, a unit that is a sealed unit for a reason. The unit your doing preventative maintenance on should out live the mower itself without service or it wouldn't have been a sealed unit in the first place. Your talking about a homeowner unit that probably wont accumulate 30 to 35 hours a year and if your mower has a decent warranty say 3 year 180 hr which ever comes first type of thing it should out live the warranty and if it doesn't it's there problem to fix or replace, if it does out live the warranty chances are good you'll probably never have an issue with the unit for the life of the mower.
See this is what I mean about someone talking about something they might not know the whole story about look up the reasons on why hydrostatic transmissions fail and maybe you understand what I'm talking about. When they fail your going to have to spend all this money to have it sent to a service shop and service by them how much money do you want to pay for that!
It says it's a sealed unit to me that means sealed to DEATH! anything with moving parts must be serviced, I don't know what you may be thinking but me sealed units is not a good enough excuse for me!
I called the manufacturer and they told me that they don't feel them prior to leaving the facility they are told by Sears not to feel them that they will fill them themselves! Also I was told that supposedly they use the incorrect weight oil which is definitely not good in my opinion that's hence the reason why they probably fail so early!
Also the manufacturer recommended that I buy another case for the bottom if I wanted to service it again making it easier for me to drain the fill again, two drain plugs one for the pump one for the transfer case!
My want to do your research before you start speaking on something that you might not know about!!!!