2-3 days. They are usually getting a bit troublesome by the end of the 3rd day, so it's not something that is really optional. Even if they seemed ok, I agree with RLK that the apparent risk of nasty infections are sufficient motivation to not go beyond 4 at the most.
You asked, so I'll reply that 7 days seems excessive to me! My reaction is that this may be asking for complications more than a blunt needle, this thing is stuck in you 24/7. Then again you have been pumping 20 years so I assume you have not run into problems?
If I were you, I would do some real research on the actual risks if a site was to actually go septic in a nasty way, seeing as you are so far out of the "convention". Then again, I'm not you.
