Refrigerant will be fine in a system as long as you have no leaks or the compressor burns out if either of these happen you will need to replace the refrigerant
Yea, I think that happens whenever the compressor is off... I`m DEFINATELY no expert, but I think they separate when the comressor is turned on and the pressure is building up. But please dont hold me to that. Theres a good chance I`m wrong.