The best way to encourage them to set up a standing order is to do it yourself. They're more likely to do something if they see that you're doing it. Let them know what kind of results you've been getting and suggest a standing order that works the best for you. Tell them that having an SO will allow them to move through the ranks unimpeded and will help them save time as well as making life easier for them. No more need to set up reminders or having to requalify over and over again.