In the past, the published schedule for Design Phase preliminary review has been a minimum of 25 business days (about 5 weeks) and a minimum of 15 business days (3 weeks) for the Final Review. The design team is given one month after the Preliminary Review to respond to the reviewer's questions. At times, there have been delays of up to 6 weeks for one or both phases, but those have been reduced in the past several months.

With recent changes to the Certification Bodies and other GBCI procedures, it's hard to know for sure, but that may give you an idea. Three to five months would be a rough estimate.