Batteries … For a mini, 4 is a good #. For a pen, I go through 2, possibly a 3rd in a single day, but you always have that extra 5-6 hours while using a 2nd and 3rd to recharge the first. 4 is good to have for a pen, using 3 per day. However, most batteries are rated at 300 charge cycles. Although, after about 175-200, performance does decrease. You should get atleast 2+ months of good use per set of batteries.

Lastly, once you get past the learning curve, mixing your own juice, prolonging the life of carts, parts, etc… becomes second nature.

Be careful and take care of your equipment, and it will take care of you!