Theres alot of factors that go on when sharpening a a knife, the metal that the blade is made out of "good vs bad steel" bad steel will dull faster.
The Angle in which your sharpening the knife at, "lets take a really good steel in this case" if i would put a 22 deg edge on it its going to feel sharp but will wear down faster, not necessarily by breaking off but wearing down by the service that your cutting
on. An angle of say 35 deg will last much longer theres more meat at the tip, when I'm sharpening a cheepo soft steel knife i increase the angle till i find one thats suitable for that blade to hold a decent edge.
Most of all when your sharpening a knife your creating a bur thats bent to the opposite side your grinding on and that bur goes back and forth as you switch sides, try grinding on one side first and feel the bur at the edge then grind on the other side and
feel the bur go the other direction, and that bur breaks off as you get a thinner and thinner edge, thats where finer grits of stone come in.
A double edge is where you would start out at 22 deg and finish up at a 28 deg leaving the very edge alittle flatter of an angle but able to hold an edge longer.