How low has your battery % gone?

I just got the t:slim and they told me to charge it for 20 minutes a day to keep it at 100%. It probably works just as well at 30% and I'm not quite sure why they say keep it at 100%. You know you can charge it from an outlet, your computer or your car. They also told me to purchase a "mini charger" in case the power goes out for any reason.