What is the limiting factor on internals in order ?
Crank, rods, pistons ?
do these engines expire easily at the limit then ?
Part of the problem is that not enough people seriously tune them to find out. There's folklore about the bottom ends failing and the rear cylinders overheating when tuned but not enough people have been down that path to build a solid picture, IMHO.
Then you have to consider what type of tuning you are going to go for. Forced induction? Hot cams, ported heads and higher revs? Each will do the job, but with vastly different demands on the bottom end.
Given that the crank is quite a complex shape to accommodate the 54 degree V angle, and the stock rev limit is close to 7K as it is, I'm not sure I'd trust it at higher revs. On the other hand, bottom end problems are not unheard-of on standard cars so how much forced induction will they take?
Answering these questions is free of charge if you pick an engine that has been extensively modified in the past, and potentially very expensive if you are a trailblazer, as you would be with this engine.
Hence the V8 / C20LET conversion tends to be the only
serious tuning you see on Omegas.