It's really hard to say. I lost the first 40 pounds pretty quickly, about 6 months, but have been stuck at 240 for a few weeks now, but part of that is I've gotten a bit lax in my diet, as well as have been eating to maintain energy levels for longer rides 60-100 miles. I have a goal weight of 185, but had hoped for 200 by years end, looking unlikely right now...but I'd be quite happy with 220.

IIRC most doctors recommend weight losses of 1-2 lbs a week.