Cell phone recommendations for a couple?

My girlfriend I are considering getting cell phones, but both of us would use them very very rarely. As far as I can tell, most “normal” cell phone plans assume you will use them a LOT and charge you $30 or $40 a month or something. There are also pay-as-you-go cell phones, but they seem to have minutes that expire. (I currently have a Go-Phone, and I keep putting in $20 of minutes which last for 90 days, and then making 3 phone calls in 90 days and wasting most of the $20).
However, I was thinking that since there are two of us, maybe we can get a “normal” plan with both our phones on it and it won’t be all that expensive per month, or something.
Any recommendations?