Yeah exactly. New bag not much more expensive either.
My oldest Rab bag is 7 years old so maybe its yet to degrade. I have only washed it once or twice though. One of the few times my congenital anosmia is a benefit!
Measure in nights or trips, not years. My MH is about 7 years also, but probably 200 nights, over 30 trips, some long ones. It's got wet a lot and been repacked wet. So it's been heavily used and in all honesty abused when out.
TBH I was looking second hand because I was uncomfortable paying for down, but if it's a liability I will just look at synthetic bags and deal with the weight.
But that's the point. Who knows what some idiot has done before. The poster can afford a new bag, so it seems safer.
My older bag is beyond best, and i have cared for it. It does not loft like it used to and the temperature rating is not what is was now.