Freon runs out depending how often or how long you use A/C in car. I live in Texas, USA where I get 100+ degree in the summer from May to September (100+ days of 100 degree).. AC is a MUST for me... My AC Freon runs out in 3 months) Unless there is leaking freon coming out from A/C compressor, It will runs out Fast! you would need to replace seals, gasket or etc.
No, it recirculates the liquid / gas. A/C's unit work by latent heat of evaporation properties of the working fluid, when the liquid refrigeration fluid goes from a liquid to a gas state it takes energy and heat travels to it, that heat comes from your house
Every system has leaks, so yes it will run out eventually.
Freon is not consumed by the system! it works due to the change of state. That thing outside has to be outside, because that is where the gas turns into a liquid again.
The gases don't wear out ... They become contaminated. While they are sealed systems, they always have a little ingress of atmospheric air, and that usually contains moisture (water). This disrupts the heat exchanging efficiency. Recharging flushes the gases with new fresh gas.
Same thing happens with brake fluid. even worse it will positively attract water. Water is a lot more compressible than the brake fluid, and will also boil ... Again, flushing the brake fluid will restore efficiency.