Cat litter doesn't do much when the gallon is almost full though. I'm pretty sure in most states now it's illegal to throw paint in the garbage if it's not in solid form. Paint seems to stay good for longer than 10 years easily if that lid is on tight. It may be pretty smelly when you open it though, which doesn't always mean it's bad either.

Waterbased paint can cause some cans to rust through in 7-8 years, will have to be decanted into a new container (and filtered)when that happens.
Oil paint in a can filled to the top can store indefinitely if you keep oxygen out.
When oil paint smells sour, it has had the oil acidify and must be discarded. Takes a trained nose to sniff that odor.
Casey

Most may be @ "Toss-out" time.
Some resin-components have settled-out, & are tough to re-integrate.

If you're lucky, & the paint seems good, stir WELL and pour-off into CANNING jars (with the separate lids & ring!).

>>> The KEY here:
MINIMIZE airspace.
Use the size closest to the paint volume!!
Use old golf-balls, or similar....to take up more room if necessary.

Faron

Okay, thanks. I'm not sure I am up for recanning the paint. However, considering the price of a gallon of paint, it may be worth the effort. I have some of those packets of paint hardener and that has worked well in the past. If the paint is hard and the can is open, my trash collectors will take it away. It's all latex.

We had so much leftover paint it was ridiculous. So one summer, we kept buying cheap walmart kitty litter and filling the cans with it and leaving them out to dry in the sun...finally got rid of most of them.

I've just been going through this. Was repainting a bedroom and found 3/4 of a gallon of the old paint--gone solid. Started going through cans and found a nice yellow, set it down on the kitchen counter to come back later to find it was leaking out the bottom in two pinholes! So I'm going through all of the cans now and cleaning things out. It was long overdue, anyway, but to find one leaking, well, that was too much. But I did find a nice leftover blue for the bedroom. :)

I would never use 10 year old paint. Today's paint formulations and performances exceed most paints more than 3 years old.

Paint science changes products too often to stick with old stuff.

If you want to get rid of paint, try organizations like Habitat for Humanity's Restore.

I've long used canning jars for latex paint. I was a little concerned about the seal given that I've seen latex paint dissolve like materials. I always put a layer of plastic wrap on top of the jar before the lid. I'd be glad to know that is not necessary. Pickle and like jars work fine too.

Most cities have hazardous waste centers where you can take your old paint (and other items not good for the landfill) for disposal

The days of cities taking paint are long gone. Sometimes you can find a place that will take oil based paint, but latex paint you are generally on your own to dispose of.

Even the hazardous waste center here won't take latex paints. You have to dry it out, adding the cat litter and putting it out in the sun to dry is a good idea.