I hear your pain... :)
Funnily enough, I'm round the other way - when I used to play as much as you do, no problems on the left hand.
If I play slightly less than I do now, a decent weekend session absolutely stuffs my fingers and I have all the issues you're talking about. I must admit I don't do much about it on the left hand - just accept it and play through it... doesn't stop it being annoying, though (and sometimes painful!).
Adam, yeah, it's the Oboe - although if there's a piano involved I'm not sure what happens, retune the 88 keys on the Bechstein/wotever... or ask the Oboe player to get a decent Oboe you can tune properly?! :lol:
Years ago, we used to have a sax player who regularly turned up to our gigs and expected to jam (encouraged by the swines on drums and keys). I had three problems with this (as did the bass-player) - first of all he seemed to regard himself as part of the band... then he wanted to play experimental blues/jazz solos on entirely inappropriate numbers (I once kicked his mic stand off the stage when he started playing :lol:), but mainly, his sax was not capable of reaching concert pitch!!! (he was around A=430). Drummer no problem, keyboard player with his little knob, no problem - but me and the bass, already an hour or two into some supreme rock and roll, adrenalin pumping, the crowd ready for the next number, and up looms our friend un-announced... everything stops while we readjust (and he's already spent 3 or 4 numbers, elsewhere in the venue, jamming along, blowing his horn as hard as he can against a wall, to warm it up and therefore raise the pitch a bit - much to the distress of that section of the audience!!)
Slight hijack there for ancient reminiscences... but, although I agree with Adam, we all seem to use "440" as shorthand for Concert Pitch - it might be not exactly right, but it's less characters to type! :lol:
Back on topic - while I was typing, I realised my approach to my left hand fingers is not to let them dry out. I have de-sensitised "hardened" finger pads. But I wouldn't regard them as callouses. If they dry out, they split, crack, etc...
This might sound weird - what about, er, hand cream to soften up the hardened stuff so it's more pliable/durable?