Sorry for the delay...
Here we are: go into IIS Management Console, right click on Applications Pools:
Page Recycling:
Recycle worker process in minutes 1740
Disable all others
Performance:
Limit the Kernel Request Queue 4000
Disable all others
Max numbers of worker processes 1 (if DNN is the only site with the only AppPool !)
Health:
Enable Pinging 30
Enable Rapid Fail enabled, following values in order of apperiance 5, 5, 90, 90
But be careful: when not unloading for such a long time, the resources will be kept for this time in memory.
Hope this explanation is ok