I don't really have an issue with this. For me, clients are reminded of their payments at the time of booking. I then also send out courtesy reminders as we get closer and tend to build in a buffer on my end.  I also have clients that opt to make payments between deposit and final lessening the burden.  For me it's just about communicating from start to finish and setting the expectations upfront even before they book with an idea of what their payment schedule for their vacation packages will be.