i got a simple question, i think. i bought a gal. of 20% nitro last summer, thinking i was going to use it all up. well, i only used about half. so my question is, how long does nitro last as fare as staying strong and good to run in our cars?

The fuel is fine. I'm in the same situation on a regular basis. If you kept it at a somewhat stable temperature with a closed lid it will be OK.

thanks, i'll take your word for it. so in that case i'm going to go and buy some new AA's and 9V's and break out the ol' rc this week end.

How well did you seal the bottle and where did you stor it? If it was not tightly sealed then just get more as it will have absorbed moisture from the air. It may still run but won't do very well.
For best results nitro fuel should be stored tightly sealed with as much air as possable forced from the container and stored in a cool, dark location. Properly stored it will keep for a year or more.

seal in org container with a tight led. stored in the bottom corrner of tool chest. dark and cool for the most part. how will i know if the fule is bad or not? is there some kind of test or a type of gauge to tell. kinda like an radiator fluid tester that has the diffrend colored balls inside. Or a burn test of some kind?

Sounds like it will be fine. Give it a good shake before you use it.
There's no real test you can do. The only way to see if it contains water is to see if it's white but it doesn't turn white until you get something like 5% water in it and there's no way you could have gotten 5% in there just by leaving it on the shelf.