From initial contact to OBLC

...some of the time frames also depend on whether a person is waiting to graduate... timing of fiscal year.. etc. If you had all ducks in a row, had your rn license and such you could do all paperwork and physical and letters of rec and such in less then a month.. and be selected the following month... probably 1-2 months lead to time to attend OBLC - assuming it landed on the right part of the year and slots were open.
The biggest lag in time I see is people 'kind of' knowing requirements and dealing with recruiters piece mail to understand and submit requirements. If you can get your letters of rec, and security packet going and have your physical scheduled..then you could make it happen fast. I'd imagine recruiters prefer to do it step by step as they get a lot of prospects that don't meet the requirements or flake out and have to manage the process in order to find qualified apps vs doing everything at once for everyone... and then finding they don't qualify.
I'd recommend taking a step back to see the general requirements - found on this board... look at your situation and assess if you think you would meet requirements... having a checklist of requirements - make recruiter contact in person - get the format he wants for letters of rec, get paperwork for security clearance and get your physical scheduled... those will get you moving quickly in the right direction.
v/r