string change for recording - how often?

Just use Elixir's

+1!!!!

took the words right out of my mouth! elixir strings sound bright as fuck for what seems like a life age!

if using "normal" strings like ernie ball etc then i would definitely change each song (that's what sneap does!). not sure I see the point in checking action or adjusting the truss rod after every string change?? not unless your changing the gauge of strings. same with the intonation really although I would be more inclined to check that. however, if you've changed your strings properly (don't take all the strings off at the same time while replacing) and you've got a decent locking bridge like a tone-pro's or whatever, then your saddles shouldn't move and therefore the intonation won't change.
 
Every song for me, changed one at time as to keep tension. I feel its just good practice, better to be safe and just make sure they're as fresh as possible rather than taking a chance.
 
every 1 or 2 songs (depending how long it takes), or every day. I don't think of string 'deadness' in terms of it sounding dull or dark... it's more about the tuning. Usually the strings start to be extra fussy with tuning after 5-8 hours of playing.
 
Just use 'em till they sound okay. I stopping going Naziesque and/or OCD'd over such issues, and I'm so fuckin' glad of not giving a rat's ass! And of course, string cleaners are your best friend. 30% Isopropyl Alchohol + 70% Pure White Vinegar shits on every goddamn string cleaner out there, in my opinion. Watch out for worn-out plectrums though :|