Gilly,
Will a dealer change the maximum time frame to something like 12 months? I doubt it because that would mean MB-USA would have to pay for four oil changes. Maybe they'd do 13 months which would limit their responsibility to a maximum of 3 services over a 48 month period.

From what I have heard, the system is set to a much longer default. If the dealer can/will set it to a shorter time, why isn't it set to this shorter period in the first place?

What I'd like is to have the FSS system set to 13 months since we don't drive all that many miles. There is no way I'm going to go beyond that between oil changes.