The timeframe suggested for greasing that belt is similar to how often you should get your oil changed in your car. Many experts suggest that you should apply some type of liquid or oil to the underside every 40 hours of use, or at least every 3 months or so. If you have purchased a model recently, you can consult your owner's manual to find how often your brand recommends oiling the belt. Some machines vary wildly, with some suggesting to oil it every month, and others claiming it only needs to be oiled once a year. The most important thing to note is that all designs need to be greased every so often! That means that if you have a hand me down model that was used in conjunction with Jane Fonda videos, or if you have a top of the line model- they all have belts that are going to requite a little bit of loving.