it does take longer, but all depends on the house, just pay more attention to the window and make sure it is clean, give it a few scrubs, u can tall just by looking at it normally, and give it a good wash down, i try to check when i have finished that they are ok
i expalin that it might get spotty, but they will go after 2 washes, the majority of people live in the real world and know that if they havent had the windows cleaned in 5 years they might not sparlkle after 1 wash,,