You need to stop doing this immediately with cash games. The Stars software is sophisitcated enough to pick up on these things and is one of the reasons why it is so well respected (and you really don't want to get banned from the biggest and best on the market). If you enjoy playing each other then you should do this via the Stars Home Games option.

I looked into the mtt thing a while back when round a mates house and we were grinding tournaments together on the same internet connection. I gather that isn't a problem if it is a big tournament as the chances of you being on the same table are slim (1000+ entrants I guess) but again, you are going to run into problems if a smaller field.