If you don't clean your strings it could be useful to try doing that. They make microfiber cloths for doing this. They also make string cleaner/ lube oils that could be helpful.
How clean is your fretboard? Can you scrap off dirt with a light pick scrape? If so you would be good to clean your fretboard. At 12 hours a day, that dirt could build up and gum up your strings. When strings go dead, it is usually from wear and grime.
How ever I have to admit .I am spit balling here, since I have not experienced the tuning problem you describe. If cleaning doesn't help, wait for someone else to pipe up. There are guitarist of all ablities on this web page. Somebody will have a good answer!
Captcha is a total pain in the........