Left work today to a flat rear tyre, figured it was a slow puncture as the tire was pretty solid when I got there, so pumped it up and rode home. Had dinner, then pulled the rear wheel off the bike, first time I've taken a proper look at it in a month or so. The cassette was making an odd noise, and there was a broken spoke on the drive side. How long it's been like that I don't know, but the wheel was still perfectly true. Set the truing stand up, removed cassette and disc rotor, everything was covered in a nasty paste of road salt, rust and other unmentionable muck. Cleaned everything as I worked around, patched the tube, put the tire back on after supergluing the nasty gash that has appeared (already have new tires on order at the LBS). Put in a new spoke into the wheel to replace the broken one, and as this wheel is the first wheel I ever built, I'm not 100% on how well it was originally built, so I de-tensioned all the spokes, then evenly tensioned them all the way around the rim. Quick final truing and it seems ok. Like @Elybazza61 I'm slowly building up my understanding of how wheels can be built, of the 4 I've built, I've re-built both of the first two, not because it was strictly needed, but because I can improve on them. Checked the chain wear, about 12 days ago it was less than .75, now it's somewhere between that and .1, so new chain time, I'll need to pick one up tomorrow.