They do stop having babies, but you can still improve their parenting skills. I swear I get skill points faster just having them kiss repeatedly and interrupting any walks to the love shack, which is just fluff anyway as the deed is done with a kiss alone. Within about five minutes I had 2 old geezers who were Master Parents! Not sure it works that well with all of them as some seem to master things faster than others, but I have managed several elders this way without losing the services of the women for 2 years at a time.