I went back to a couple of Arban exercises I'd not looked at for a while with a view to possibly incorporating them into my daily routine.
One of them was Pg. 21 Ex. 47.
It's two 16 bar phrases and aside from a crotchet rest halfway through, I'd previously found it pretty difficult to find other places to breathe. Sometime or other I'd marked in 3 addition places where I could snatch a quick breath, but they were hardly natural.
More than a little surprised this evening to find that I could get through it fairly comfortably with just the one breath in the middle. I was taking it at a pretty pedestrian pace (maybe 112 or thereabouts), and can't come up with any explanation other than a change in the amount of tension between then and now.
In which case tension has a much bigger effect on the length of phrase you can play in comfort than I'd imagined.