It took 6 hours each for our first two games because of rules lookup and my friend is more AP prone than me (his competitive nature and my cross referencing of BGG added greatly to this).

I have good intentions for the first hour(keeping the rules for reference nearby and looking stuff up), but my friend is especially competitive and wanted me to be extra sure we did our best to play correctly. For myself personally, I would try not to worry about playing 100% correctly the first time through (time permitting).