The heat of a 150 degree oven is not all that hot, relatively speaking, as ovens can get pretty darn hot.
If you do not set the paint, the jars will begin to peel and be ruined. If the oven is too hot, the jars will break and be ruined. So, the way I look at it, it is worth the chance to put them in the oven to set. I would put them in a tray or line the bottom of the oven with tin foil so if the jars break, the glass will be easy to clean up.