I agree that it's probably not a good idea to switch crank lengths -- routinely or infrequently -- especially if the length is increased for a hammer-fest up a climb.

Sheldon Brown and Andrew Bradley say that longer cranks can't provide extra leverage when gears are invloved. This is Bradley's opening statement on his site (http://www.cranklength.info/cranks.htm):
"If you know anything about physics you will have realised that more crank leverage, of itself, does not mean "more power". Any power gains via crank arm length would have to be due to physiological reasons." And these are Sheldon Brown's thoughts: "this is a common misunderstanding. The "leverage" of a bicycle drive train, also known as "gain ratio" depends on the crank length, wheel diameter and the sizes of both sprockets. Yes, if you go to longer cranks without changing any of the other variables, you will have more "leverage", which is another way of saying you'll have a lower effective gear...but on a multi-speed bike, you can change gears at will! Ay, there's the rub! Assuming you adjust your gearing appropriately, crank length has no effect on leverage, it just has to do with the range of motion of the knee and hip joints." http://sheldonbrown.com/cranks.html

But I reckon otherwise coz I've accidentally put myself in a blind study (n=1 ) using longer cranks without realizing it, and then wondering why I was flying up hills.

Some pros use longer cranks for time-trialing (Indurain used 190s), and Marco Pantani, the diminutive Tour winner, used 180mm cranks for mountain stages, but he spent a lot of time off the saddle on climbs, obviously negating a possibly compromised seat height. Other pros used longer cranks for mountain stages.

So, I don't care what the 'doctors' say, I reckon long cranks = more leverage