Extend animation

Hello.
I have animate my Watersurface between frame 1-250 OK.
I would like to extend the animations to frame 502 but still animation stop on frame 250. Why
I try to change to linear and constant in Key - Interpolation mode but that dont make any difference.
How can I extend water to move all the way from frame 1 to frame 502.
Thanks
Karl

http://www.pasteall.org/blend/14634