I hate that term "sealed for life". You usually find a non greased bearings life span is a lot less than a greased bearings.
But this is a good tip and will check ours next time i go to the storage unit. It was last serviced by Fiat to keep up the warranty but that does not mean they greased the rear axle, the interesting part is the service interval is every 2 years but this has to be greased annually. Unless it was greased as part of the habitation service by the dealers and that was annually except last year because they were shut.
Not unless there is a good planned maintenance system.
The most expensive form of maintenance is lack of maintenance.