.. dear STW dear STW..
It had a slow puncture for ages and ages, 18 months perhaps, then it started to get a little quicker then it became quite a bit quicker suddenly, so that it went flat in about two days. At this point I put some tyre weld in it thinking I was going to get winter tyres fairly soon, and it how holds air. However the other day I found a nail in the tyre right at the edge. Doesn't look as if it's been there for 18 months though.
So - repair the tyre, replace the tyre, or leave it.

