Where I work, the right seat guys are tested to, and expected to perform to, exactly the same standards as the skipper. Most of the crew in the right seat are there because of time in the company, not because of lack of ability. Indeed, many of our crew have the seniority for a command, but opt to stay in the right seat in order to remain on their chosen base.
A few years ago I was talking to a very senior FO and when asked what about a command ? His reply was " I will loose so much income as I currently have first choice of routes ( expenses)"
I recall a well known FO on Concorde getting his command on 737s.
I am comfortable that the guy in the right hand seat is up to standard.