CP is time based, also refered to as the Point of Equal Time, it changes only with wind (moves into wind).
You can have Multiple Points of Equal Time- Normal, One Engine Inoperative, Depressurised, Two Engines Inoperative (Yes only on three or four Engine A/c).
Aircraft generally burn more fuel following an engine failure or depressurisation.
The important thing is to have the Point of No Return at or beyond the Point of Equal Time.