There is an interesting blog by Naveen Padrang titled XI : How to Re-Process failed XI Messages Automatically which you can read before you continue with this one.
I would like to highlight the section that talks about IS_RETRY parameter and how he wishes to tune the parameter. The solution he mentions is to change the default values of the parameter in Visual Admin.
I am running SAP PI 7.1 EHP1 SP 03 and guess some of the wishes have come true in a better way (if I may say so).
Note: The feature is available from XI 3.0 SP19 / PI 7.0 SP12
It is NOW possible to control the Delivery attempts directly from RWB and whats better is that it can be controlled per communication channel and thus avoid a global setting.
Guess this might come as a relief for numerous real time scenarios that demand controlled Delivery Attempts !!!