[Dbmail] postgresql migrate 2.0 to 2.2

[Rod K]

I'm currently running dbmail 2.0.11 on a live server with about 15GB of 
current email.  I need to upgrade to 2.2. 

The problem is that the postgres migrate script is going to take a long 
time to run with that much email and really, really don't want to take 
down the server for that long.  Is there any issues with leaving 2.0.11 
running while migration is going on or once complete before shutting 
down 2.0.11 and restarting with 2.2?

TIA