Compressing and QT movie at the same time

Hi, has someone tried to make a QT movie while compressing another QT at the same time?
I am working with avchd files (Transferred to appleprores with toast), doing 2 -3 hour weddings. Make QT Part1(self-contained), then send to Compressor and instead of waiting a couple of hours, can I start making QTPart2? at the same time? . Just wondering if someone has tried this. I noticed that getting in the internet while compressing can cause problems some times, so I usually wait for Compressor to finish, but time is money now. Gracias amigos!

Johnny
imac i5, 10.7, fcp7, 8ram

(I always make a self-contained QT and then send to compressor)

Johnny