Thanks for the link Katie.

I'm surprised to see any recommendations that don't depend on the context of the team. My answer is a strong "It Depends".

I've worked with teams that forced the pair switch every two days (we were working 10 hour days four days a week, so the math worked well). Our work was pretty granular too, so stories could usually be completed within two days. Other than that one project, I've never forced swapping.

I think the swap frequency depends a bit on how big your stories are. If your average story takes 2 days, then swapping with less frequency seems to me to be too frequent. Of course, forcing many folks on the team to be exposed to a given story can be beneficial; I'll have to stew on that.

Per John's recommendation, inspect and adapt is always good advice. That is - try some reasonable frequency (let the team decide) and revisit the frequency on an iteration basis. Also consider that the team may consider that forcing a time-based swap frequency is not right for them (swap at story boundaries instead perhaps - adds complexity in timing swaps of multiple pairs).