Getting Clients to Keep Coming Back

I am launching a new coaching business focused on public speaking and presenting. My target market is introverted professionals who have to regularly present or publicly speak as part of their livelihood and their success. I have created several programs- intensive and refresher courses for my clients but I’ve created my program to make them feel totally confident and comfortable when presenting or speaking publicly.

My question is this: how can I get clients to keep coming back for more coaching?

My concern is my business model is set up for one-time only clients who occasionally need a quick refresher course (much cheaper than my initial program), but I’ll have to keep finding new clients to make a lot more money.