This depends on 2 factors; which show your ad runs on and how many episodes your ad is assigned to. The key in deciding this is understanding the difference between total episode listens in the first 30 days and total series listens in any 30 day period.
The former is the total number of times a single episode is listened to in the first 30 days from the release date.
The latter is the total number of times all episodes in a show are listened to in any given 30 day period.
If your campaign allowed for 10,000 listens and a recently released single episode was getting 10,000 listens in the first 30 days, if your ad is only applied to that single episode, the campaign would last approximately 1 month. If the ad is applied to the 2 most recent episodes, the campaign total would be reached faster, perhaps in 2-3 weeks (please note it is difficult to give exact figures for past episodes as the data is only provided for the first 30 days of release).
The dynamic ad insertion system we use is automated, so we set up the campaign with a total listens limit and once the campaign is live, your ad will appear in the requested roll position on the agreed number of episodes until that limit is hit, then the ad will stop running. We can also set an end date for the campaign, after which the advert will stop running.