I am a lady of advanced years( 65 actually!) working in a famous British supermarket on the Delicatessen counter. This week it has been unusually hot over here and although we have air conditioning my Mistpro 3 has been invaluable and I have had to share it but even so the water lasts a long time. However, I was surprised to read that one should use distilled water. So I have knackered my guarantee by using tap water. Hey ho! It still works though so thank you fir such a great product. Goes nicely in my pocket or hand bag.