Actually I’ll take that back, the disk speed doesn’t matter that much.
I have a similar machine except it’s a Mac, the i7 is 3,4Ghz, it has 16 gigs of RAM and a thunderbolt raid with 500 MB/S read and write. Encoding an hour of full HD PNG Quicktime would take me about 9-16 hours (on the render estimate) so it could easily take 26 hours.
I’d suggest getting the DNxHD Quicktime codec and trying that. It works on any OS and can hold alpha information.