There are a great many people that enjoy hunting for a partner rather than keeping them. They feel trapped by the work involved in maintaining a relationship. As soon as they believe their partner has settled in comfortably, they begin to feel the urge to find a new partner. Dumping the old partner is just clearing out the hunting cabin for them. There is a way to keep a partner like this, but it is does involve some work. If nothing else, it shows them a bit of what they do to others.
Keeping a partner that is a serial dater is accomplished by not letting them know they have truly achieved their goal. Keeping this type of partner on edge is often accomplished by taking the time to be seen with other people on dates. They will continue to work towards achieving a relationship until they know it is in the bag. Moving on is always reserved for a time when the relationship is truly established and they feel trapped by maintenance.
One way to find dates quickly and easily in this case is to contact an escort agency. They specialize in accommodating many different types of requests. A simple night out to be discovered on a date with an unknown acquaintance is a fairly easy request to fill. Most escorts would be able to handle this type of request without a problem. Even an independent escort would find it to be an easy night's work.
Serial daters are often selfish people that care little for the feelings of others. Once they've seen their partner on a date with another person, it is best to end the relationship. It may hurt the serial dater, but it is no more than what they would have done eventually. It may even teach them what they are doing to other people.