I'll disagree with ALL of the above - just for sport.

First of all not all 119 motor wiring harnesses go bad - a lot of cars make it to the salvage yard with the original, and many more will. This is not to suggest that they are high quality parts but they last longer than 104 HFMs for two reasons - they aren't exposed to the extreme heat of actually being routed into the engine as with the HFM 104s, and secondly it is a much less extensive harness and there is considerably less need to disturb it. 104 harnesses have to be disturbed at the spark plug cover for head gasket repairs and even just to change spark plugs. This causes failures at that most heat exposed portion of the harness. 119 don't have head gasket failures and it is not necessary to disturb the harness to change the spark plugs. So the harness can keep chugging right along even with insulation in pretty sad shape.

119 motor harness aren't that expensive - $400 to $500 if you shop around, and installation is no-cost DIY. This is not that big a deal compared to head gaskets, new trans., evaporators, throttle actuators, and even 104 wiring harnesses.

I've heard of failures of the lower harness but it seems to be less common. I've had four 124/119s and never had a failure or even a sign of deterioration. A lot of these originals are going to make it to the salvage yard too.

What goes on at a 500E forum isn't likely to be germane to the real world.

The point is you don't have to replace a 119 wiring harness just because it's original - it might well make it to the salvage yard, which could be next week given the market value of the cars. Backing into a light pole could total it. You don't want it to show up at the salvage yard with a bunch of shiney new parts.