You are in fixed operating mode. From my reading on this site and my own experiences, I would say no, it is not common for the computers to fail. This is good because they can be picked up cheap used.

Do a search on ECM (the computer I THINK you are talking about) and look for my recent post (10%=..).

You can do some testing yourself with a few cheap tools and the info on this site.

good luck.

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E