I believe I remember Rush said he stopped playing his (hilarious) song parodies when he went deaf. He wasn't able to hear the parodies, so he stopped using them. Which was sad for Rush's listeners, including me.
“He wasn’t able to hear the parodies, so he stopped using them.”
It seems like a lame rationale for Rush to have used. He couldn’t hear bumper music anymore and that continued. Although he “heard” the music through memory.
He had Snerdly or his wife and even Shanklin himself whose judgement he could have trusted on new parodies. Ending them was a decided loss for the show. Plus the targets of those satires bitterly resented them.