I am doing hourly work. But this is for clients I have high level of trust. They believe me. Most other clients are more concerned to know fixed amount of time

I am doing hourly work. But this is for clients I have high level of trust. They believe me. Most other clients are more concerned to know fixed amount of time and if project took less - they want to get it back, although I negotiate that successfully so far =) The worst case is - estimate in hours. =)