How long can you store unused paint

[68charger440]

I painted my car with DuPont Centauri about 7 years ago.  I have about 1/3 of a gallon still left. 
Is there a shelf life or is it good indefinitely?
Also, I have a wave that I want to get rid of. Can I put 3 or 4 coats of clear coat and sand that to get the wave out without touching the color underneath, and then put a final clear coat on top to get the shine back?  Or do I have to get rid of the wave first underneath and then repaint with the original paint?

[Canadian1968]

I would probably say that paint garbage. If it was sealed AIR tight .... maybe but  I wouldn't risk it. 

Your "wave" what is it from ? Is it body work?

It doesn't really matter, because the only way to really get rid of it is to block it out , you will most likely go threw clear in to color and probably down to metal until its gone. Will need to be primed , block again and then repainted if you want it completely gone.

Spraying multiple coats of clear to try and fix it is asking for trouble. First you will probably get solvent pop from amount of clear you are applying . Second, when you put clear on it doesn't fill the low spots and level the high, its just going to build up evenly ( the wave is still gonna be there ! ).  Your trying to use the clear like a high build primer, it just simply isn't ment to be used like that.  Your going to try and block this wave out , so you will have this glass like area where you are trying block ( which will also high light any other flaws you didnt' see at first ! )and the surrounding  area will have the natural orange peel of the original finish, maybe be more noticeable than the wave you were trying to get out !!!

Not to mention I am not sure what color the car is , but clears have a slight amber tint to them for UV protection , you could now be fighting a color problem , along with the wave !!

If it bothers you enough, there is only one way to fix it .

[68charger440]

The car is the red one showing on my profile picture on this thread.  It doesn't have any clear on top of the red Centari acrylic enamel that I painted it with.  I gave it four pretty heavy coats so I can probably block it a fair bit without getting through it all.  The wave is not real heavy, it is just from where I didn't block it good enough originally on one side.  Would I be better off blocking it off and buffing it back to a good shine and then only priming and painting that section again if I do cut through down to the primer or metal?  My thought on using clear on top was just to give me a little more room to sand before cutting all the way through the color.

[Dino]

There's very little imperfections you can buff out or fix with clear.  You'll go through those 4 coats before you get rid of any visible wave in the body work,  It's enamel so I say block it, prime it, and shoot it with urethane this time. Your old enamel is no good any more by the way.  7 years is way too old to reuse it.

[68charger440]

Is urethane better than acrylic enamel?  I'm not a paint and body guy so I don't know much about the products in use today, but I can spray pretty well.

[Dino]

It is.  Enamel is not horrible paint mind you and it has its uses, but for a few bucks more urethane will give you a stronger end product.  Enamel will still do the job if you're on a budget, just don't use lacquer.