Well the recipe calls for 1-2 primary and 2-3 secondary (pretty standard) so your total in "primary" will be 3-5 weeks if you hold to the recipe. Personally, I wouldn't let the oak chips sit for longer than 2 weeks so I would handle it as such:
Either wait for the airlock to become nearly motionless, or use a SG reading to determine the end of "primary" fermentation. At this time add the oak chips and let it rest for 2 weeks after that. This will be your "secondary." I think you should be fine with that. If you want to stretch it out to 6+ weeks. That is fine, but I wouldn't add the oak until the last 2.