Medium. The restaurant business is hugely volatile, and with only 1 in 8 restaurants surviving to year 4, odds are high that you will have to move around a lot to find a place that is stable and pays.
However, you may have a little something to do with your own success. Patrons of fine restaurants will give your place repeat business if they feel they’ve struck gold with you. So if you know your stuff and consistently hook people up with the right wines, you could become “that brilliant sommelier at Chez Lapin we love so much.” Who wouldn’t want to help that guy keep his job?