I also think maintenance is a function of ones personality. I know some homeowners who are always keeping their houses up to date and maintained properly. Other just do not seem to do too much. They live in them and do very little to them.
The same is true of RV owners. Some just maintain the RV's better than others. Some will repair broken items and others will just live with it broken.
I guess you would need to look inward and decide where you fit into the above.
On our class c, we basically take care of the front end which is a Ford e450 v10 triton (oil change, etc) Then, on the backend, we have the generator, ac, tires, etc.
Like vinmaker said, lots of it depends on you.
Some folks deduct it as their second home or as a business expense. If deducting as business, repairs and maintenance need their own column.
Don't have a MH,but I think of maintenance costs as a savings.You keep things up,they last longer and if your going over your rig,you can find things that need a little fixing up.Fix it before it breaks.