6 months or 3k is a good schedule to shoot for, even if you go over a little, no worries, if you go under, no worries, the car just loves it, my 99 with 67k on it has gold Toyota oil, all the time... runs like new.
ProfessorP deals with smart mechanics.

 

on my other 2 cars, my Acura MDX - every 6K to 7K miles (usually every 4 months or so in my case) and my Lexus ES300h - every 10K (synthetic oil) which unfortunately I hit every 5 months or so as well. So my seldom-used 97 Lexus ES300 is the only one where I have to worry about time-frame.

 

This is a very interesting video about engine oil, that's worth watching.