More info:

One tree is a Juniper Foemina, the other Juniper is a Procumbens Nana.
We had a really hot and dry summer, but I did my best to vigilantly water them every day or so.

Thanks!

Conifer trees can be taken care of in terms of winter care the same as Deciduous Bonsai. They go dormant the same and once they are in heavy dormancy do not need any light.

For care of my outdoor bonsai I keep them in the garage after they have gone dormant. I prefer this method since you can control the temperature better and protect the tree more from unusually warm days or ones with extreme temperature drop as well as cold drying winds which can force the tree to transpire too much moisture essentially drying it out and killing it (which is a prominent problem for me because I have a field in my back yard). If you decide to do this make sure to store them off the ground and to keep them twords the outside facing wall of the garage and not by the connecting wall to the house. when you water make sure you do so more sparingly and to not saturate the soil as you might during normal growing conditions. You will only have to water a fraction as many time as during the summer also. Ideally a dormant bonsai does best between 30-50 degrees. They can withstand short time periods bellow but if they are in these conditions too long the root ball can freeze.

As far as enjoying them inside you could bring one of the Procumbens nana bonsai as an indoor bonsai to enjoy it during the winter as they can survive up to zone 9 conditions. This does raise some problems though that need to be taken care of properly for the tree to stay healthy and happy. The tree will need to have adequate sun and that it receives a lot of humidity which can be supplemented by the use of a humidity tray. It would also be best to keep it in a room with a higher humidity like a bathroom (if possible).

Keep in mind This is just my opinion and experience since I live in the Chicago land are (zone 5) and can have quite harsh winters some times dropping to -10 degrees. I'm not familiar how the weather is in your zone but I'm sure you will have to be less vigilant as the weather in your area is more mild. Hopefully some on closer to your zone can help with some better suggestions.

Good luck.

-Mike

Thanks very much Mike. That answered the bulk of my questions. Quick follow up: do you know when or under what conditions Juniper bonsai enter "dormancy" or "heavy dormancy"? Is there a way to tell (other than no new growth? Thanks again.