8 years? Christ, that's longer than any civvy relationship I've had, let alone a WG!
Stick a link up, sit back and read all the reviews from your punting brethren...seeing countless other guys plough through her should help disattach some of the emotion.
Harsh, buy true.
And yeah, I'd say if her service has become lacklustre it's probably as she may know the score. Or she's just completely taking you for granted, she sees you as a cash cow, a regular bundle of twenties and nowt more.