The time the SCEA takes is largely based on how long it takes you to complete the assignment when you're doing other things at the same time. I think, had I had nothing else to do, I could have gotten it done in two work-weeks during normal business hours. (As it was, it took me about three months in the evenings, but factor in that I was doing the SCEA assignment after work and while planning a wedding.)
You can search the forum for more information on what's involved in the Part II assignment.
Theodore Jonathan Casser
SCJP/SCSNI/SCBCD/SCWCD/SCDJWS/SCMAD/SCEA/MCTS/MCPD... and so many more letters than you can shake a stick at!
If you can get to work on it for a considerable amount of time (say 3-5 hours) a day then you are probably looking at completing it within 2.5 months. If you only have weekends and evenings to spare then it might take longer. It also depends on how comfortable you are with your design. I changed mine about 3 times by adding/removing layers where necessary
Obviously, the amount of time taken by a candidate to create a solution to the assignment varies greatly. A fast candidate might create a solution in about 40 hours, but a more typical time requirement might be about 80 hours. If you spend a lot more than 100 hours on the project, then you might be creating something that is more detailed than the requirement, or you are lacking some of the skills necessary to complete the assignment.