I always think you should always "plan for the worst" and "hope for the best". For every 2 week turn-a-round time there are a dozen 4 month time frames with the majority being somewhere in the middle.
The following is from the State Department's website:
What to Expect:
Effective October 8, routine service can take up to 14 weeks from the day an application is submitted to the day a new passport is received.
Expedite service (for an additional $60) can take up to 10 weeks from the day an application is submitted to the day a new passport is received.
These door-to-door timeframes include both our processing times and mailing times on the front and back end.
Select Trackable Mail:
Send your application to us via USPS Priority Mail Express and pay an extra $17.56 for 1-2 day delivery of your completed passport. These services provide the fastest turnaround and protect your important documents
State Department Passport website