[johnb]

I'm not super across the evidence on pair programming so I'd hate to try and have a definitive answer. https://www.cs.utexas.edu/users/mckinley/305j/pair-hcs-2006.... suggests it's pretty good for quality and so-so for utilisation.

My anecdotal experience with my own teams is relying too much on pairing as a training mechanism, especially between senior and junior, has a couple of issues. The first is tradeoff between training quality and utilisation - it may shorten the training cycle but the payoff isn't high enough for the output constraint on the more senior member. The second is I've sometimes had trouble weaning the junior off always having guidance on tap and it takes them longer to develop confidence to break through certain problems alone.