Verizon: How long till I can upgrade?

i hate my phone, the buttons dont work anymore and its only been a year since we signed a 2 year contract. we have 4 people, sharing 1400 minutes. i have 500 texts a month. one person has a data plan. one person has a smart phone, the rest are feature phones. can anyone determine when i get an upgrade? for the discounted price that usually comes with a new contract. thanks :)