Liquid is CO2 at approximately 58 Bars of pressure.
The pressure increases with temperature, which is why the speed of the pellets changes with temperature.
Under normal atmoshperic pressure, obviously the CO2 exists as a gas.
In order to liquify it, you have to pressurise to about 58 Bars.
In order to get sloshing there has to be a gas above a liquid.
The CO2 under pressure can not exist as gas because the pressure is too high.
Instead it exists a liquid/gas state.
So the liquid/gas expands to fill the volume inside the capsule.
The CO2 remains in this state until the volume of CO2 drops to 30% of the original mass of gas.
This is when the power drops from shot to shot.
If you keep the ambient temperature the same, then the CO2 will produce exactly the same power from every shot, until you have used 70% of the mass of the CO2.
If you keep the temp constant and wait for CO2 gas to return to the ambient temperature between each shot, then you will have get very close pellet speeds from shot to shot.
Obviously this depends on the airgun you are using too.
My heavily modded Crosman 2240 was so consistant, the fps deviation averages out to about plus or minus 1/2 of a FPS.