I am having a hard time coming up with a scenario in which a sharp, large decrease in my standard of living makes wireheading a more sensible thing for me to do.

I do sympathize with the urge to do it even if it isn't sensible -- ditto the urge to drink habitually, have unprotected sex with strangers, faff about on the Internet while at work, or shoot myself in the head -- but I can't quite grasp that as a long-term plan, either.