How long will it take for SSA to decide my case?

This depends on many factors.  If you get approved at the initial level, it could take only a few months.  If your case has to proceed to an ALJ hearing or beyond, it could take 2-3 years or more.  The strongest cases with the best medical evidence obviously get approved easier and faster.  However, it seems Social Security is getting tougher and tougher each year.  We find that most people get denied at the first two levels and have to proceed to an ALJ hearing before they prevail.