As Bertie says, it's a common problem in UK and is potentially a killer!
I always keep an absorbent microfibre cloth to hand to help clear windows in conditions like this.
The worst case is a night departure on a cold, night, where the aircraft is cold soaked and the occupants bring extra moisture into the aircraft. It's best to turn the heat on full (pull some pitch to get N1s up to give enough airflow if necessary) and wait on the ground until the windows are cleared and will stay clear on take off.
The checklists for twin turbines often call for airbleeds 'OFF' for final landing checks, in the case of single engine failure. My take is that losing visual reference on short finals in a fully serviceable helicopter is far more dangerous than the tiny possibibility of an engine failure, so I sometimes keep the heat on if the conditions require it to keep the screens clear.