I have an Avon Redstart (hypalon) we originally bought as a tender to the RIB, and for the last 12 years have used on the sailing yacht. We've owned this boat 16 years now, and bought it a year or two old, so probably actually 18 years old now.
It's stored deflated in it's bag all year round (out the sun), inflated only some weekends in the Summer, and kept inflated for 3-4 weeks on our annual cruise. We wash it off in fresh water when we can, and try to put it away dry, but that's it! It tends to get a decent clean once a year if it's lucky with a sponge, fresh water and maybe some soap, but no special polish, protectors or anything.
It still looks as new, and the only thing I have had to re-glue (once) is the valve in the inflatable floor, because it's position is such that people keep standing on it or kicking it, which I don't think helps!
I'm sure keeping it softly inflated might be better for it and less taxing on the glue/seams, but like many people, I can't realistically do that. I'm hoping to get many more years service out it yet, as it's such a perfect tender!