Actually, if you did saturate the charcoal bed you may find out before the next time you fill up. As the gas is pumped out of the tank the tank breaths in through that charcoal bed that everyone is alluding to. That’s its only source of air to replace the gas removed. If the bed is saturated, a vacuum may form in the air space and make it difficult for the pump to pump gas out to the engine.
If after your tank gets below 1/2 full you begin to have loss of power or operating problems, remove and replace the gas cap. If you hear a whooshing and the problem goes away, it’s a safe bet that you’ve saturated the charcoal and the tank can’t breath in.