As the sibling comment says: my VPS is always on, and I can SSH into it from any of my machines, reattach to the screen session, and talk under the same nickname. Besides this, I'm never offline (barring things like netsplits). I'm not doing it for security reasons, although it does provide a level of indirection if your goal is to not expose your home IP address to everyone (getting a cloak is also useful when it comes to this).