50 months are required with CURRENT hardware, when ASICs will be deployed it will shorten a lot! The time required to complete the accounts will depend on the difficulty by that time, however it may be as short as 2 months.
As I told you before, by mid april I'll have a prototype running, for full deployment expect mid/end of may.
50 months is more than four years!
How much can one expect to make on average?