How long ago were the eggs laid? They can sometimes take up to 2-3 weeks to develop eyespots. They will look like 2 tiny black pinpricks near the middle of the egg. Additionally, if you see the yolk start to condense at one end of the egg, it can be a preliminary sign of fertilized eggs.
For the lifespan, I would say that if your octo is laying eggs, she probably only has another month or two left. Some bimaculoides remain small through out their whole life so it can be unreliable to estimate age based on size. In order to extend lifespan as long as possible, continue to feed her regularly and, if possible, slowly drop the temperature of the tank a few degrees. It may kill the eggs (if you aren't planning on breeding them then you won't have to worry) but you may get another 3-4 weeks of life depending on your current tank temperature. (you can safely drop it to about 61F without harming the animal).