Adding new Touch to household... question.

[(vikm)]

Adding a new iPod to the household. It is a Touch and I have a quick question (or more). Is it better to add and use it under my existing iPhone/iTunes account or keep it separate by registering a new user. My wife will be the main user. I was just wondering if I've purchased an app for my phone if you are required to pay for it again to use on the Touch. That would be the main reason I can see to use the same account but if it's not permissible then it's probably better to keep them separate.

Thanks.