When you make a change to the ica listener in the remote session host configuration, then settings only stay applied for between 30 to 60 minutes. Then the settings reset to default. This is because Microsoft do not support changes to the ica listener and you need to use the citrix tool.
This is generally an issue with xen app5.0 or 6.0 on Microsoft server 2008 R2
Ok so we need to set the correct settings via the ICA Listener Tool which is under your default citrix program folders.
So click on Start > All Programs > Citrix > Administration Tools > ICA Listener Configuration.
You will then see the application below.
Edit the ICA-TCP settings and set it to your desired limits. This will resolve this issue.