At a lower temp, brine shrimp just take longer to hatch. What I do is set up two cultures with the second one set up about 24 hours after the first. Then alternate them.
I think it's a lot easier compared to setting up a heater or light.
The quality of eggs you use has a lot to do with it. I've found that you are usually better off getting them from an online supplier, rather than your LFS where they may have been on the shelf a long time. If the eggs get damp, they are a lot less likely to hatch well.