Routine maintenance does not need to be done by the dealer to be effective.
Examples -
1988 1/2 Ford Escort. Around 175,000 miles when my son traded it in on his Mustang. Serviced exclusively by Jiffy Lube. Oil changes, transmission service, coolant, etc. Had a few mechanical issues late in life, but one of the most trouble free cars I've owned.
1997 Jeep Grand Cherokee. Presently around 175,000 miles and running fine. Serviced exclusively by Jiffy Lube. Other than running longer than 3000 miles between oil changes it gets whatever service (coolant, transfer case, differfentials, transmission) their computer says it's time for. Just put a 4th set of tires on it a month or two ago. Top end Goodyear Wranglers as I expect to wear them out in about 60,000 miles or so. Before the Jeep isn't economical to keep on the road.
1999 Jeep Wrangler. About 115,000 miles and running fine. May have to replace the spark plugs (factory installed) one of these years. Again, Jiffy Lube for all routine servicing. If it needs it, it gets it. Again, a very reliable vehicle. Stranded me once when the fuel pump gave up without notice. That tow job paid for several years of AAA membership.
I'd hate to add up the receipts each year for Jiffy Lube alone, but the way I see it, it is still cheaper than buying a new engine or vehicle every few years. While I admire much about my great grandfather, his "Buicks are greased at the factory" attitude about vehicle maintenance was faulty.
Elizabeth, I think the whole point of the replies in this thread isn't that you shouldn't have stuff done to your MB on a proactive basis, it is that the dealership probably isn't the most economical place to have it done.