My experience has been that very few people run the FSS out to the limit on the time factor, usually it's run out on mileage.
I would recommend that if you put very low miles on the car to just remember to change the oil once a year if that's what your concern is.
For what it's worth (tell me if this seems wrong to you) I thought the early maintenance system was called ASSYST, and the later versions (around 98 or so) were called FSS. Was the online owners manual for a current E Class (211) or maybe an early 210 chassis? Maybe they still use ASSYST nomenclature in Germany.