Membership expiration variants

Hello, i want to set up a video tutorial site where people can access each video for a different prices and expirations. So say i have 4 vids ,each will have a different price. Then after the person purchase i want him to have access for a limited time eg: say Today Fred buys vid 1 for $20 , i want him to access that vid for only 20 days .but 7 days later he purchases vid 2 for $30 and will have access for 30 days. Is it possible for the 20 day vid to expire as planned or we cannot have multiple membership levels?