Most of the time it's only 7 or 8 feet up.
A local window cleaner Squeaky knows (John H) slipped off a sloping roof, some years ago, while trying to get onto his ladders in the local army married quarter estate and broke his leg.
He couldn't have fallen more than 8 feet.
The next time you bump into him, ask him; he tells a funny story about it.
Squeaky, don't climb them; especially when wet. Just knock some cash off the price; or just bill them the same amount and don't mention them; or use an extention pole and do a 'best effort' with it.