Where PPB' s have emerged from finished hardwood flooring although it is presumed they will not lay their eggs on the finished wood, is it reasonable to suspect that the Beetles may seek to re-enter the floor at a flight or exit hole to lay their eggs? How many eggs will a Beetle lay at one time? Once emerging as a Beetle what is the life span of the actual Beetle?
Powderpost beetles emerging from a wood floor will have a hard time relocating their exit holes so it's not likely this will happen. In the wild where wood is untreated, they'll have access to entire pieces of lumber. But in the home, most of the floor will be finished making it impervious to the eggs. This means they'll have to locate small holes over a terrain that's basically sealed tight from intrusion. Furthermore, there will be all kinds of "scenting issues". You see, in the wild, wood releases odors and scents which PPB can target. A lot of these odors are dependent on moisture.
In the home these odors have a hard time permeating like they do in the wild. No doubt the air in your house is a lot dryer which will limit the scent and odor given off by your flooring. Furthermore, it's highly likely that all the other scent in the home will distract the adults from finding what they normally can find easily. But lets say they could; even then it will be very hard for them to locate pre existing exit holes.
Now once adult beetles emerge, they must find a mate before reproduction can begin. Again, in the wild this is relatively easy compared to the confines of a home. But even if they did mate successfully, it's likely their egg production would be "low" compared to the wild. That being said, a female typically will lay 25-50 eggs. In the home where conditions normally are more dry and "harsh" for PPB survival, they'll most likely be laying less compared to egg production in the wild. Now remember, I'm assuming you don't have ideal reproduction conditions in your home. Over the years I've seen homes which were serving as PPB generators because there was a lot of moisture and other variables helping the beetles. My point is some homes will "help" PPB but in most cases this doesn't happen.
Lastly, the life span of an adult is generally a few months to a year with few living more than a year. In the home, it's hard to say but estimates are low meaning most likely just a few days to a few months at most. Again, this would be based on a "healthy" home free of conditions conducive to insect infestations.
In fact all your questions and concerns kind of "reinforce" the general practice of leaving wood floors untreated when adults emerge because it's generally hard for them to continue the life cycle on the same wood. In other words, active populations tend to die out unless they have enough wood moisture and a good supply of wood on which to lay their eggs. Read more on wood floor infestations and how to treat for them in our WOOD FLOOR TREATING section of our in depth article about powderpost beetles.