The nose bolt on my Swallow keeps undoing on its own. After about a week I can put 3 or 4 complete turns on it with bare fingers. I should really put some threadlock on it and sort it out once and for all.
You do need to be very careful not to overtighten it, which is very easy to do, but the whole "don't ever touch the bolt" is a bit over the top (too many people take Sheldon's words on this as gospel, and not wishing to sound callous, but he's not around any more in order to revise them).
Without tightening the bolt on mine I would have had to have binned it. The leather had dipped enough that it was touching the rails. By re-tightening it I've saved it, and it's served me perfectly well for plenty of long distance rides (including 1400km of London-Edinburgh-London) and shows no signs of damage. I think I've been careful enough not to overstretch it. I usually only use the spanner to put in 1/4 to 1/2 a turn on top of what I can do with my fingers.
I'd say that some saddles (remember that no two bits of leather are going to be the same) may need the occasional tweak every so often, but unless it's slackened off on its own, we're talking 1/4 of a turn of the bolt at a time, and give it a minimum of 3 months between each 1/4 turn (i.e. max 1 complete turn a year). Most of the time one or two tweaks will sort it out and you'll never have to touch it again for years.
Tighten it too much and you'll cause the leather to stretch. Once it's started to stretch it'll only get worse, it's much more susceptible to stretching/sagging, which starts the slippery slope of requiring more turns and more frequent turns and before long you'll ruin it (you'll either reach the maximum extension of the bolt or, even more obviously, the leather will begin to thin so much it splits/tears).
Over application of Proofide will also cause premature stretch if you ride on it after softening up the leather too much. The main job of Proofide is to replace the natural oils that get leached out when the saddle gets wet (either from rain or sweat). My Swallow sees a small application of Proofide every 6 months or so when the saddle is starting to look dry enough that it's becoming scuffed up along the edges.
Anyway, I really should get some threadlock...
P.S. Brooks Swallow. Coming up to 3 years old in February. 20,000km in all weathers. Stored indoors but gets the occasional drenching outside when I'm in playing 5-a-side, playing football or riding it. Has done individual rides on it where it's been heaving it down for 20+ hours.
