Sea Monkeys Yet to Hatch?

I got some sea monkeys for my daughter as a starter pet. I followed the instructions exactly; cleaned the tank, added 10oz distilled water, added the purifier and let it sit for 24 hours, then added the eggs.

We added the eggs around 8pm Tuesday night and I've yet to see any babies. I'm a bit bummed since sources say it should only take 24-48 hours. It is a bit chilly in my house (its winter and we keep the heat around 69 Fahrenheit) but I do keep this regular lamp on for light. Should I get a heater or is this normal? What are some things I could do to encourage hatching?