I just finished a film where the mixer was using a Cantar and we came across the same issues of burn time. Namely with the poly-rotate burn, the times for burning were just too long. We had production buy 2 hard drives, and would copy to the hard drive between takes. Then at the end of the day power down the machine, unplug, hand off, and go home. In the morning we would get a hard drive back, plug in, and go. It made life a lot easier and post was happy as well. After we started doing this we never heard a complaint about files not being able to be read or bad disks.