Tony, I'll copy the response I sent you earlier via your DM.

Your portfolio is a representation of how you solve design problems and express creative ideas.  It is not something that gets assembled over a specific time since it's not usually a collection of work assembled for just a portfolio.  Most will take several years of work and compress it into a few dozen pages.

Thank you very much. But I meant that i already have plenty of projects. I just meant time to rearrange them and compress to several 30 pages. with adding or subtracting some renders or etc.

How much time you put into it will be completely up to you. I think most people spend too much time on their portfolio. More is not always better. Reviewers tend to look through these things quickly and are probably looking at the forest rather than the trees (in a manner of speaking). 

My recommendation would be to come up with an overall idea/vision of what you want the portfolio to be. Make a plan to accomplish it, and stick to it. Don't get sidetracked by redoing things just to make them look better for the portfolio. If, at the end, you have some extra time you want to put into it, go back and solve the 1 or 2 things that really bother you about the portfolio. But again, don't lose the forest for the trees.

I agree with the above comments.  Leave a little bit of time before the deadline to distribute to 2-3 trusted reviewers and time to pick up their comments.  It would help if your reviewers were also the ones writing your rec letters but they do not necessarily have to be the same people.

I spent about 2 month concentrated working on portfolio before deadline (while I am still in school)

More the merrier

This depends a lot on how good you are at these sorts of things.
Start, and you'll be the best judge of how long it will take. 

When do you plan to submit your application?

Subtract todays date from that date. That's how long it will take.

A curmudgeonly perspective: I did my portfolios over winter break, 1993.  My last day of class was December 17, the application deadlines were January 4 so I had to Fed-Ex them by January 3, and I had to visit family for Christmas from the 23rd through 27th, so I had about 12 working days.  I applied to 6 M.Arch programs, assembled and bound each portfolio by hand, xeroxed text onto my pages, cut and spray-mounted every image, and Letrasetted 6 covers and spines.  Given that today I would be able to eliminate all of that assembly time for 6 separate portfolios, and all the many walks to Kinkos to resize, copy, and print images and text, and all the packing and shipping, it could all be doable in 2 days.