Hi,
I use the AppKeepAlive on a lot of sites and it works very well. Some hosts force application pools to restart at specified intervals, regardless of whether or not they are dormant. I would assume your host does this if the AppKeepAlive doesn't seem to be working for you.
If your host does force app pools to shutdown, there isn't much you can do to remedy the problem and any .NET application you run on that host, will have this problem.
HTH,
Joe D.