yes, if you know the homeowner is going to replace, and you are the "last option", then going that aggressive might be necessary.
one thing to consider doing is, before you jump into something which could damage the carpet, just let the client know as much, and feel them out. that way they can let you know if they would like to keep it for 25 more years and can live with how it looks...or not
Follow-up to this story:
Yesterday I received a phone call from these people.
I thought: "Oh no, the carpet all fell apart right after I left their house". No, not at all. The wife told me that they thought I deserved more money for the job than I had charged then (It was just about $300, took about 4 hours, and they had given me a $25 tip)) and she said that she had sent me an additional $100. She also wanted to know if I cleaned upholstery as well. When I told her I did, she scheduled a second appointment to have three sofas cleaned. (I don't think I'll use the Fibre-Max pads on these, but, hey, you never know!)