Better solution than a GO-Phone?

Hi All!
I need some advice. See, I live in France and visit the US often and when I come home to the US I need a cell phone so that I am not completely dependent on my mom. The last time I went out I bought a Go-Phone by At&t... we all have At&t in my family, so it makes sense to have an At&t phone if possible. The only problem that I am having with the Go-Phone is the fact that the SIM card expires abour 90 days after the last bought minutes expire and I am not in the States every 3 months.

I asked if I could buy a new Go-Phone SIM card (instead of the whole phone) next time I come out and they said no! Which means that I will have to buy a new cell phone every time I go to the US and I will have no idea what to do with the old ones!

Do you know of any other pay-as-you-go cell phones that I could use that won't expire so quickly? I come home sometimes 2 times a year, so a 6 month expiration period would be better.

Thanks!