concerning ownership of arcade games

I have a delightful problem.  I have one 360 in a household of two game players and it is just not enough 360.  I see a conflict developing between me and my fiancee over gaming time.  I'll be purchasing another 360 as soon as the zephyr comes out and getting a live subscription for my fiancee so we can play on live together.  I know my arcade purchases follow my gamertag but what about my fiancee playing the arcade games I have purchased with her gamertag.

Do my Arcade purchases cover the household and the multiple 360's I will own?  How has M$oft handled the issue of multiple consoles and players in a household in regards to Arcade games? 

you have to rebuy them unless you have a non updated 360

i tried using a memory card but it just gives trials