Well at least at PSA the absolute most Senior FO you'll fly with as a Captain will be right about 2 years. That's about the maximum time you can avoid the forced Senior Upgrade.

So the times of having an experienced FO in the right seat to catch a new Captains mistakes are well and truly over.

I've been on property for 3 years and that puts me in the top third of the company which is nuts when you think about it. I make sure to tell all my FO's to absolutely speak up and we'll help keep each other out of trouble. I know other new Captains though who like to lord their four bars over the new guys, and they convince these FO's to just sit there and shut up.