Processing large IDOC SAP 4.6c - WM IS 6.01 - Java 1.31.01

We are experiencing problems with the transfer of large Idocs from SAP.

Large IDOC = > 20000 segments

Is there anyone doing this routinely and does not have to restart
the IS instance every 4 or 5 days ?

If so could you please provide your Hardware/OS/Java configuration

We have tweak our Java configuration but always end up using all the available CHeap.

thanks, Mario