When talking about the length of time that products should last one should also take into account how the item is used and stored.
I try to look after my gear but sadly I didn't look after it that well when I stored it in my loft which unfortunately had a leak and soaked the kit, not much lasts in those circumstances.
Of my new gear I expect all of it to last at least 10 years, the TT and speakers maybe 20 years.
My issue isn't really over the length of time that items last, it is about the ability to get it serviced/repaired at some point in the future, parts within an item can fail and being able to get this is rectified can improve the longevity of the item.
From my meagre knowledge of the HiFi world I am unsure how many companies could service one of their products now even if it was a relatively young 5 years of age. I believe that Linn, Naim, Rega and probably a few others can look after products from yesteryear and beyond but if you look at the kit you have how confident are you that each manufacturer could facilitate a service or repair on those products?