Is an offer open for acceptance forever?

No, an offer is not open for acceptance forever. An offer has a limited lifespan, determined either by a specified time limit stated in the offer or by the conduct of the parties. Once the offer lapses or is withdrawn, it is no longer capable of being accepted and a contract cannot be formed. An offer may also be terminated if it is rejected, if a counter-offer is made, or if the subject matter of the offer becomes unavailable.