The historical recommnended 19 min 50 sec e.max speed crystallization fire time is the one that I have been using.  There has been a shorter one being pushed that is under 13 min.  

The research conclusion of the under 13 min protocol is now being documented.  Two primary issues, less than full crystallization shift from the metasilicate to the disilicate leading to more opaque ceramic and rougher surface finish.  Will this be a significant ceramic performance issue over time?  Don't know yet. The under 13 min cycle is not recommnended by Ivoclar.

November 1, a new 14 min 50 second cycle will be avaliable only using a new firing tray and spray glaze and no more than two restorations at a time.  No loss of ceramic quality has been documented with this new time.