80% of my welding is on 18 gauge or thinner material. I just find that the smaller wire does a nicer weld on thin metal, but still works fine on metal up to 3/16". Of course, you use way more wire than with .030, but the trade-off is worth it for improved weld quality. I Always use the 10lb rolls, but it does not sit on my machine very long. The small rolls of wire at HD are a pretty poor value. I was waiting for a roll of wire to arrive on the big brown truck and ended up having to buy a roll 2 lb roll of wire at HD, and realized that I would pay as much for 4 lbs of wire at HD as I would for a 10 lb roll from the welding supply. I usually go through a 10 lb roll pretty fast, so corrosion on the wire sitting in the machine is not a problem. It is not at all unusual for me to go through a 10 lb roll in less than 2 weeks, as I do a lot of fabrication.
Regards, John McGraw