I assume you mean a criminal case? There is no limit. However, the more adjournments the stronger argument you have for not receiving a fair trial - memory of the witnesses will fade in time, the length of time someone of good character has this hanging over him, the importance to the public in bringing the offender to justice are all matters which should be taken into account. If the trial is being constantly adjourned you should make strong representations - however, if the trial date has not been fixed, you have a weaker argument.