November 22, 2011 4:43 PM EST
I think they are just the same level as you whenever you pick them up, so if you went and got another one it'd probably be good for a fair few levels.
Personally playing as a Thief I just got annoyed after getting the same old "I don't think you should be in here" from my own companion, so I dumped him almost straight away.
Oh also just to point out I just use my invincible horse Shadowmere to tank dragons and the like so y'know that's always useful. To me the companions in Fallout:NV was much better, bit more of a storyline etc I found.
Though I do use the temporary companions, like conjurations (mainly the old assassin) when in need.