For me, the cups are fine even when it rains, just dont take the pi$$ with them or do anything too erratic! Its only standing water anyway you really have to really worry about and again, when I had that on the motorway, I just eased off and no problemo.
If you are doing a lot of track days the cups won't last long but I think you should have to have at least one set of cups during your ownership to be able to compare to the rest !
Again, will depend on your mileage - I dont do loads of miles so mine have lasted me well and are only now borderline.
You can get a set of cups for around the same price as PS2's and if you are really friendly with your dealer.. you may get them trade
I cant really comment on the PS2's as I only used them for a short time after I first got the csl and before I really got to know the csl
properly