Best way to have creep spawn points but not have camping?

Anyone have an idea as to how to have a creep spawn point but not have players justing camping there and killing the creeps?

In my first map, I just had people enter a region and the trigger checked if there were any creeps in the region and if there werent, then creeps would spawn. This obviously leads to players camping.

My second map I had it on a timer of three minutes and if there were creeps in a region already, the trigger did not make more creeps at that region.

An idea that I have not tried and just thought of a few minutes ago was to have a large region over some land mass (but not include towns in these regions) and then have creeps spawn at random locations (such as create 5 gnolls at random location in region azeroth) and have a few of those per region. I think that that would reduce or even eliminate the ability for a player to camp at a creep spawn. Then when all the creeps are elimated from a region and some time has been met (3 minutes) more creeps would spawn in random points in the region).

Any ideas?

Make a very large region that covers a large area where you want those units to spawn within and have it spawn monsters in a random point in the region, so the heroes actually have to look around for monsters because they will keep spawning in different places. Also put smaller regions in the middle of tree clusters, water, or other unreachable areas and such and make a trigger so that if a unit spawn in any of those regions it is removed and respawned at another random point.

Why not try to make instead of the same creeps spawning over and over, make them get harder and harder with every spawn. For instance just make so everytime they spawn it adds 1 to variable CreepLvl, and when that creeplvl gets to 10 or something, make it so it spawns harder creeps. You could add this to Dinadan87 suggestion and it could work very well.