Like any new service offered it's just a matter of gaining experience as each job is different. Some can be a doddle to do using a guttervac and others can be a real pain in the arse.
Once you start going over the height that ladders can't reach safely then should something go wrong or you can't do the job properly by guttervac for whatever reason that’s when you can start getting into alot of bother.
I remember one lad on a forum mention on a commercial job getting his nozzle stuck in a downpipe (including his camera on it) 3 storeys up.. Whilst he tried to get it out the top section separated from the rest of the pole. Oops!
Don't think the firms H&S bod was too impressed as was left sticking out like that for a few days until the chap could get hold of a long enough ladder to retrieve it.
Needless to say he decided to pack it in after that.