When I see my subs (which is only once every few months), it is usually for 3-4 days at a time with the play sessions lasting several hours (with varying intensity) and bondage being almost constant.

I think as a kidnapping scenario that could also work... But, it is a shitload of work for you as the Domme & means almost constant vigilance which is really exhausting as time goes by. Because of that, I can definitely understand limiting it like you do.