our stair carpet as basically had it, it is ten years old and the cheapest you could buy back then so I think that we have had our money's worth out of it, but now it is threadbare and it's come unstuck from the second to top step so it's getting a bit dangerous
carpet cleaner won't bring it up but we could nail or glue it back down to make it safe...which is what dh thinks we should do (when I see we I mean me 
I think that rather than have a manky looking carpet on the stairs and landing we should pull it up, bin it and see what the stairs are like underneath....I have pulled the bit that is loose away and the stairs need cleaning up, but I was thinking I could gloss them?
Can't stain them as someone must have had a runner at some point and there is white gloss for about three inches either side of the steps
we cannnot afford a new carpet anytime soon would be a couple of years as there is more dire stuff that needs doing
so wwyd stick with a dirty carpet or take your chances with how bad the stairs look...