As the community above have indicated, there is no fixed timescale, and it does vary geographically, but roughly, its around 2-3 weeks for the Tribunal to log the initial appeal, another month or so for the DWP to prepare the bundle, and another 4-6 months for the hearing date. Citizens Advice have some very useful info on their website https://www.citizensadvice.org.uk/
@lulubell - I presume your ESA appeal related to a fail to attend an appointment/return a form/change of condition? for an ordinary 'didn't score enough points' ESA appeal you can receive 'appeal rate' ESA once your appeal is logged if you have a sick note...?
@lixsharp13 - @Matilda is right in saying that the Tribunal are only allowed to consider you as you were at the date of the DWP decision under appeal - this means that deteriorations in health cannot be considered, and sometimes can be harmful to appeals in that if the Tribunal feels you only just meet the criteria now, they may assume you would not have at the time since you state you were significantly better. If the deterioration is significant you could think about making a new claim on this basis as well as the appeal.
Hope this is of assistance.