Verizon $5/mo renew method has changed?

I have two MiFi hotspots. One is a 4620L and the other is a 6620L. The Verizon voice prompt used to say if I did not pay within 90 days of the expiration date I may lose my phone number. Since the 4620 is basically a backup, I decided to let it expire then refill 90 days later. I still had internet access 90 days past the expiration date. I then added $5 and the expiration date advanced to 30 days past the date I refilled. I had 4 months of service for $5. Right now I am 10 days past the second expiration date. I have been refilling the 6620 every month through CallingMart. I will continue refilling the 4620 every four months and see what happens. If I lose the account I would have the 4620 reflashed. I have not used the Verizon Inpulse Refill yet, but will have to do it come June 30.