1. Try not to expose your mascara to too much air. The more you leave your mascara open, the more it will dry out. Mascaras that come with a thin brush tend to live longer as the tube opening tend to be smaller.
2. In case your mascara got drier, instantly add a drop of water or baby oil to it (depends on the base of your mascara). This way you will moist the fluid and make it easier for application.
3. Always store your mascara in a relatively cool place. By being exposed to heat or sun, your mascara might dry out or even get ruined. Read more on fustany.