on-call rates

[Dirk Koopman]

I have been asked to make myself available "on-call" 24/7 (for defined 
periods of time) on third line support on a product that rarely goes 
wrong. Nearly all problems are infrastructure or user cockup. However, 
said users are a) paranoid about blame and b) by default, it must be our 
product's fault until proved (*PROVED* I say!) it isn't (99.9% success 
rate on that so far :-). Oh, and by the way, *please* get us working PDQ 
(pretty please).

I believe I might get called 1->4 times year. Are there any standards or 
bits of common practice out there that can help me price this up?

Dirk