Mercedes has extended the emissions related warranty to 10 years, if the unit has had the AEM. Look for a label on the underside of the hood.
https://bluetecupdate.mbvans.com/con...Disclosure.pdf
I have a 2016 Sprinter - I had 4 MB warranty repairs, 2 NoX sensor failures, ambient air sensor(covered under emissions), one rear wheel speed sensor (safety recall). The RV has 69K miles, I put 30K of those on the unit. I have had no significant issues.
On the house side, there have been many many repairs. From simple fixes to replacing a slide mechanism. Fortunately, I'm skilled enough to do the work.
If I had bought an extended service plan, it would have been almost worthless.
Just knowing that the RV would be sitting in a dealer lot, waiting for a diagnosis, then waiting for the authorization from the plan, then waiting on parts, then waiting for a service appointment made the decision easier for me.