Mine was extremely fast - 3-4 days between enrollment application and approval for interview. Interview itself was available at LAX
the following week so the whole thing was done in about 2-weeks. As I recall they send you and email to your registered address once the application is cleared to proceed to the interview stage.
Off course I might not be the typical applicant as I have some 20+ years of established Federal government background history with various security and military clearances so the typical experience might be different.
Anyhow once you get it can be a big time saver. A couple weeks back I was off the airplane and outside on the curb in under 5-minutes. Nonstop walking from the plane with under 60-seconds spent at the kiosk. Amen.