The Bessa-R has a bit more plastic than I would like to see in a camera. However, in some cases, plastic can absorb impacts that would leave a dent in a metal plate.
One of the things that I've heard from other users is the markings. All of the indicators, including the marks for frame lines and even the name of the camera, are painted on rather than engraved and then filled. On some cameras, the paint has worn away.
On my own Bessa-R, which received very gentle use while I had it, the paint was beginning to wear away after three years.
Aside from that, there is the usual issue of deteriorating foam in the channels of the back after 10 years.
The shutter is an all-manual Copal and seems reasonably durable. The rest of the mechanics aren't that complex, although I imagine a heavy-handed user could damage the film-advance mechanism by forcing the advance at the end of a roll.
I never took one apart, so I don't know how much plastic gearing, if any, is used. Hopefully, there aren't any.
Overall, I think this camera should hold up adequately for day-to-day use.