Generally, the defendant (Social Security Administration) has 60 days after the plaintiff (disability claimant) files their complaint in District Court to file a complete transcript of the actions taken and testimony given before the agency.
After that, the plaintiff has 30 days to file a brief containing legal arguments and statements of fact.
After that, the Defendant has another 30 days to file their brief containing legal arguments and statements of fact.
Either party may ask the court for an extension of time to file their briefs.  Generally, the court will grant an extension of 30 days at least once.
Once all the briefs are filed, typically it takes the Court approximately 6 months or more to issue a decision.