The time a DSP will keep an audience can vary among DSPs,  The Trade Desk, for example, flushes all their audiences every 30 days, requiring you to renew that audience or it automatically deleted. Other DSPs will keep the audience in your seat forever.

OnSpot has automated republishing and schedule options to ensure your audience stays available for serving in whatever DSP platform or social network you are publishing to. Read here for detailed instructions on republishing and scheduling options.