Well, since I'm one of the people in the "non-
ventilated bag" camp, I should probably say a few 
things here...

Yes, I'm of the opinion that ventilating your 
cels will cause the lines to fade.  I generally 
don't get up on a soapbox and preach about it, 
because I only have my own experience to go on, 
and there's always the chance I could be wrong.

As for the "gases" released from a cel, the 
question is really whether the off-gassing comes 
strictly from the paint or from the reaction of 
paint and air.  If there is no air to act as a 
catalyst for this reaction, would it still 
occur?  Do you really want oxidation to continue 
long after the paint has dried?

I also worry that ventilated bags will allow in 
dust, humidity, cat hair, tiny insects, etc.

If you're worried about gases building up in your 
cel bags, then my suggestion would be to open up 
the ends every once in a while, press out 
whatever air is in there, and then reseal the bag.

As for sticker residue, the best thing for it is 
to "fight fire with fire"... or in this case, 
fight sticky tape reside with a piece of sticky 
tape.  Just put a piece of regular transparent 
tape over the sticky residue and then peel it 
up.  The tape residue will stick to the new tape 
rather than the cel, because the new tape is 
stickier.  Press, peel, press, peel, etc, until 
all the sticky is gone.