I have over 300 colours on my rack, many are over 20 yrs old and they all spray fine if I want them to.
The #1 cause of spray can trouble is our failure to shake em up.
Keep in mind that with spray bombs the pickup tube rests smack-dab in the middle of an inch of gummy paint sediment at the bottom. Just because we don't pry off a lid and get forced to mix it in .... doesn't mean it ain't there.
I've seen guys pickup a 2 year old spray can and give it a little "test shot" just to see if it works. Can you say instant pluggage?
If you force yourself to shake an aerosol, upside down, for a minimum of 2 minutes BEFORE giving it that little "test shot"

...you'll rarely have trouble.
This being said, I've found Rustoleum aerosols to be the biggest challenge. I suspect it stems from the high concentration of solids they give you (a good thing) but they always need an extra minute of shaking and sometimes I have to still clean the nozzle with compressed air a couple times before they cooperate.
Soaking the can in some warm water for a few minutes does wonders to make it spray better as well...the warmer fluid becomes thinner so it atomizes finer & seems to dry faster.
Finally, before recycling empties remove the nozzle buttons and toss em in a little jar of lacquer thinner. Before long you'll have a ready supply of clean nozzles in case one plugs up. There's 2 or 3 different sizes.