Blocked downpipes? Can't be done by me, all I can do is push the nozzle down as far as the s bend. I sometimes use a drain jetter on domestics. At that height I could use a fifty foot jetter from the bottom if they hadn't put a kink in the run of the downpipes :

I don't have a fifty foot jetter - only thirty foot so I'm buggered really on this job. I don't think a pressure washer with gutter attatchment would do much more to be honest.
Early days still for me - i'm still learning.
Pole became mega heavy with sludge - I nearly lost it trying to lower about thirty five foot horizontally.

No sign of any wear on the poles - been using them for well over a year now.