The one making an offer is considered the “master” of the offer and can dictate the terms of acceptance. If the adjuster made an offer that expired in 30 days, then technically it cannot be accepted after that because it no longer exists. However, insurance companies generally are under a duty to investigate, adjust and settle claims reasonably. If you were to contact the company, explain the situation and state your desire to accept the offer, it likely would be unreasonable for the company to turn you down. The duty of reasonableness applies to all aspects of claim settlement, including the amount of payment.