It is up to you how you'd like to spread out your orders. We are going in late January and I am going to start ordering a few vouchers (5 or so) at a time every 6 weeks or so until I have all that I need. That way I have them prepaid but I don't have one big bill. It also depends on whether you plan on joining just for the $1 month trial which would mean you'd need to order as many as you'd need during that month. If you plan on keeping the membership, you can spread out the orders as you like.
I have found the Connections program to be very dependable and they deliver very quickly. There have definitely been those who reported problems so be sure to double-check your bills etc. to prevent any double-billing. I think if you are persistent and conscientious about keeping up with your charges etc. you should be able to prevent any serious problems.
Good luck!