We did the cut, harvest and removal for 3 days in a 9-10 acre lake last April. We were able to cut the weeds approximately 5 feet below the surface . We have not cut since. We will cut again this April / May when the water is at it's lowest level. So the answer is about 1 year. We believe this method will continue to slow the growth with each additional yearly cut. Also it is becomes easier to cut as you learn the depths of the lake and it's hidden underwater obstructions, such as dead trees.
Is it expensive? For small ponds and lakes I would think the expense is the most important issue, especially if it's a private pond and one owner situation.
