The reason the tank needs to be cold when filled is a bit complicated.
A 12oz CO2 tank hold "12 counes of liquid CO2".
The pressure in a CO2 tank is the same, regardless if it has 1 ounce or 12 ounces. It is also the same pressure as the BULK tank, regardless of how full it is.
So, if you were to try in fill a WARM 12oz tank, what would happen is liquid would transfer into the BULK tank to the 12oz, but as soon as the liquid expands, the transfer WILL STOP because both tanks will be the same pressure.
Usually, you can only get about 10% capacity into a WARM tank.
So, why a cold tank? CO2 is VERY temperature sensitive. A warm CO2 tank is about 1000psi. A cold CO2 tank is around 400psi.
So, if you fill a COLD co2 tank, the pressure will be about 400psi, and the bulk with be about 1000psi, and the COLD tank will try to equalize the pressure by PULLING in liquid, until the tank is full, or the pressure is stablized.
This is why it is hard to get good fills in the winters. You don't just need a cold tank, but a tank COLDER then the bulk tank.
Anway, who ever is FILLING the tanks will CHILL it AT THE FILL STATION. This is done by putting in a couple ounces, then quickly draining. This will chill it enough for a full fill. You DO NOT need to chill it for them.
Dou you get more shots with a warm tank? Depends on the gun. A warm tank has a higher pressure, and greater energy, and therefor needs less CO2 to push a paintball to 280fps.
You can leave your tank in a freezer as long as you want. Why??
You can store your tank ANYWHERE you want. However, if it is FULL, I would suggest NOT storing it on your gun, or anywhere hot (ie near windows, or in your car). Otherwise it might blow your safety valve.
My ******* nonsense
"the evidence strongly suggests that neither Billy nor Adam (Smart Parts) could have invented the electronic paintgun" -Garr M. King, U.S. Judge