Weather Induced Swelling Of Deadbolts & Other Mysteries

The thing I find slightly baffling about the design of my otherwise well laid out, spacious home is the way the doors are configured.  Ok, the front door is where one would expect it.  Nicely positioned between the double garage up & over, and the front room window.  There’s a porch affair in front of the door offering a little protection from the elements and on the whole, it’s stood up to over twenty years worth of everything that’s come it’s way.  However, every suix months, I have to file down one of the deadlock bolts a fraction when it starts to miscue on it’s way into it’s hole – due to excessive sun and rain at certain points.  It’s the back door that amazes me.  It is down one side of the house, off the utility which in turn is a tiny room iff the main kitchen.  I do like having a separate area for the laundry and hot water boiler etc, but my house points the wrong way to attract sun first thing and this side pathway is always shady and unappealing.  The back door however has remained in absolutely fantastic condition since the day we moved into the house, spanking brand new.   I guess the fact I don’t open the door so often, I have not exactly overworked the deadlocking system and the door sits snugly in it’s framework without any catching, binding, suaking or other unfortunate sign of wear and tear.    Much to the disappointment of the suppliers of replacement doors and windows.