Hi James,
just because they 'shacked up' doesn't necessarily mean that there will be eggs. Turtles are kind of like people when it comes to 'mating', sometimes they do it just for the heck of it. However, keep an eye out and be prepaired! How big is your female? If she's a full size adult, she needs to be in something larger than a 60 gallon! If the weather is nice outside, you really should think about building her and her boyfriend an outside enclosure. Anyway, expect eggs in about a month. It should be easy to tell when she's gravid, you'll be able to feel the eggs if you place your fingers between her plastron and rear leg. ~Christy