You can reuse gel wax melts because no matter how many times you burn them, the gel will not evaporate. However, as with any other type of melt, the fragrance will expire over time, although it will last longer than melts made from soy, beeswax and more traditional types of wax. You should expect a gel wax melt to give you up to 40 hours of burn time, as the gel has a much higher melting point. To get the most out of your melt, turn it over after every use (ensuring the gel wax melt has cooled) so the fragrance can disperse evenly around the room.