I have no problem carrying a Twist with a filled T2 attached all day, but I use a lanyard. So it holds it upright.
In my experience, all the T2 I've had leak, leak from the top when lying down (hence, the tissues in the drawers where I store them, filled) I've never had one leak from the battery connection end.
On the other hand, if you do happen to get even a small leak, if it gets in your eGo button, the eGo is probably ruined. I'd hate for you to lose a brand new battery that way (and "user abuse", which getting liquid in the button is, is not covered by the warranty)
My own personality is better safe than sorry.
It's really up to you.