Instead of or in addition to 10 day roaming add-ons for the US (e.g. talk, talk + text, data) why not create 1, 2, 3 week or 1 month add-ons?
10 days seems to be a slightly arbitrary number of days. And why not give users better value if they are traveling for longer?
I'm going to the US for just over 3 weeks. I will be spending 2 days relaxing before heading to a campsite retreat where no phones are allowed. So I will be only able to use my roaming add ons for 2/10 days. But a month long add on could offer me better value. Also I won't have the hassle of having to renew the add on while I'm enjoying my time away.