I see there is a service bulletin about the long crank time required to start my car. However I do not see any information on how to rectify the problem.
I had the same problem with my 2005 Sentra. I took it in for routine oil change (at the Nissan Dealer) and asked about long crank time mainly occuring during hot weather. They advised there was a service bulliten. They replaced the Fuel Pressure Regulator at no charge.
Battery problem, battery cable connections (clean and tight) or fuel pump would be my guess.
Try this, turn the key to the on position but do not start. Wait a few seconds, then turn it to start. If it starts right up, its the regulator.
This is the process truck drivers use when starting their semis. You could just do this all time, and you wouldn't need to fix or replace anything.