USA: Best options for multiple trips?

[PhotoJim]

Pony up for T-Mobile. As suggested, if you have to, spend $10 every 3 months to keep it active (or more if you run out of time, of course). Once you've hit $100, your next topup will extend expiry by a year (if you put in $100 immediately at the beginning, you get a year of validity instantly). Also, it roams at the same rate within the US, so even in areas without native T-Mobile coverage it's quite usable.