Acoustic Guitar Construction

Can anyone advise me on storing a gallon of Emtech 6000 once I've opened the can and have taken some out?
I was at Target's web site placing the order for a quart when I noticed they ask for a promotion code to buy it cheaper.
The code is AX3G to get 20% off. That might apply to more products than the 6000.
The price for a quart including the 20% off and the cheapest shipping is $33.64. For the gallon with discount and shipping, it's $57.14. So that would be $25.50 for the other 3 quarts.
At any rate, I'm going to spray it this time and don't anticipate using all that much.
Several questions:
1. If I'm careful and don't get any on the rim, when I close the lid, is that all there is to storing?
2. Any idea how long it will last and not get thicker?
3. Is it helpful to spray something "inert" into the can just as I close it, to keep regular air out of it?
4. I have a garage with a shop behind it, but neither are climate/humidity controlled. Can I leave it there with no bad effects, or should I leave it in the house, maybe in a closet?
Thanks for suggestions,
Bob

I've left mine out in the garage for months and it seems to be fine. Wipe out the excess on the rim or it will rust. Some of the new cans I think are all plastic. I'm talking about the EM6000. I use this lid which has worked better for me than the lids that come with it:

http://www.rockler.com/product.cfm?page ... te=ROCKLER

They now have the quart lid and I have 3 of those and fill the quarts cans as needed.

Thanks, Tim. I just remembered that I had some touching up I needed to do to my first guitar that was completed sometime in 2010. It might have been last year, and the lacquer was still good. Can't remember if it was as thin as when new or not. But it was thin enough for that job.

This stuff works good and is well worth the few bucks