It's hard to pinpoint exactly how long a court-martial will take, but an experienced military lawyer can give good approximations of how long your court-martial will take based on several factors.  First, what level of court-martial is the Government pursuing against you?  We are usually referring to Special Courts-Martial and General Courts-Martial if you are even asking this question of how long it will take in the first place.  A Summary Court-Martial is generally scheduled for a specific day, so you, as the client, will already know how long the court-martial will take because the date of the hearing will be scheduled.  In a Special and General Court-Martial though, charges are preferred by use of a Charge Sheet, which gives the accused notice of the specific allegations which the accused is being prosecuted for.  A Special Court-Martial is widely considered to be preferred for misdemeanor-type charges, so offenses that are general less than 1 year of confinement time, and that result in no worse than a Bad Conduct Discharge ("BCD") characterization.  Generally, Special Courts-Martial take anywhere from 4-6 months from the date of preferral all the way through the end of the trial, which means from the time of receiving the charge sheet to the time that the accused gets the verdict, or finding of Guilty or Not Guilty.  On the other hand, a General Courts-Martial is typically convened with charges preferred because the allegations reach they felony-type level, such as for sexual assault, serious assault and battery or domestic violence allegations.  General Courts-Martial generally take 5-8 months from the date of preferral all the way through the trial.  More serious charges are taken to General Courts-Martial.  This is not always the case though, there are some Military Justice shops with JAG at differing installations that may hold a different policy of preferring everything to a General Court-Martial.  General Courts-Martial can be the procedures for both misdemeanor level and felony level type offenses.  Understand that the Military does not use the terms "misdemeanor" or "felony", but State Courts typically see offenses with a punishment of less than 1 year as a misdemeanor and those that are greater than a year as a felony.  As a result, General Courts-Martial will take longer because the UCMJ requires an Article 32 Preliminary Hearing to determine whether or not probable cause exists before sending charges forward to trial.  Additionally, because General Courts-Martial consist of more serious allegations, counsel will likely have requested the appointment of experts and their schedules also have to be factored in to scheduling the trial date.  Moreover, their appointments have to be approved by the Convening Authority.  The more serious offenses, the more likely that the trial will involve more complexities.