It is necessary to have a generator in a 5th wheel, I know some have them some don't. We are looking to go to a 5th from our class a and we really don't use ours a lot now.
Love our Onan 5500 propane generator. We used it a bunch on our trip to Alaska. No worries about a portable disappearing. We also have a 2000 watt pure sine wave inverter. We are truely self contained. We "exercise" it once a month and change the oil and filter once a year. That is the extent of the maintenance.