I think oil seals are very likely to go on any brand of car and any engine if excessive crankcase pressure builds.

If the rebreathing system is maintained so pressure is controlled, I think seals will still just go time to time, though probably infrequently.

My examples: On a 240 I lost a camshaft seal shortly after buying the car used from a dealer who had sold the car new and serviced it. It was clear that the rebreathing system had never been maintained (at 64K miles). I don't recall if I ever replaced a main seal or not on that car (200K miles). On my 850 I have carefully maintained the rebreathing system and flame trap. In 132K miles there has been no sign of leak at main seals. However I replaced the rear camshaft seal on exhaust side, which was leaking very badly. The seal when I inspected it in place was cracked, very brittle and dry.

On other cars I have seen what appears to be seepage from main seals but never lost enough oil to do anything more than watch it occasionally. Of course your level of concern will depend on your need for absolute reliability, for instance driving in remote areas.

Some earlier posts indicated a design change was made in the 850 rear main seal but I have not looked into that.

No direct info on gearboxes - my 240 and 850 both use(d) Aisin gearboxes with zero trouble except for PNP switch (gear position sensor) in both cars. Fluids changed at 60K intervals or so.

My impression from watching neighbors with cars stuck in snow is that some drivers will try very hard to shorten the lives of their automatics.