Terri, where are you? How cold is it getting? At 8 months old you'd have to be somewhere ridiculous for them to need a heat lamp.
Terri, where are you, north or south of the equator? I hate to make assumptions, I'm often wrong. If you are north and the days are getting shorter that could have a delaying effect. If your days are getting longer that could help. Or do you use supplemental lights to extend the day. A red heat lamp on all the time doesn't count. They need their down time so a bright light on all the time could hurt.
With all that said, they are going to lay when they lay. I've had EE's start laying at 18 weeks, I've had EE's lay their first eggs at nine months. That was early December with the days about as short as they are going to get yet still getting shorter. All the rules say that won't happen, yet it did. The rules are not ironclad.
No one can tell you when they will start. Real life doesn't work that way. Instead of a heat lamp to keep them warm you might put a light on a timer to add some length to the day, that might kick-start them by making them think the days are getting longer, but with my 9 month olds I did not do that.