i have a 25ft pole, and manage most 3 storeys, only if they are really set back can i not get them, but thats sometimes down to the access to them also.
it's absolutely at its limit on a fair few windows on my round, and it's fibre glass, so flex's an awful lot, reducing the amount of pressure i can apply to the glass, which worries me as to how clean i can get some of them...however, no complaints so far, so not too bad.
i will be investing in a 30ft carbon pole once i get a bit of free cash.