I refilled my 3g Verizon plan today using a $5 PIN. My renew date was Dec 14 but decided to do it early just to see what happens. My renew date went from Dec 14 to Jan 9. My balance went from $10 to zero. It appears it's best to wait until the end date to renew. I did my previous renewal one day before the end date.
On a disturbing note, a new message has appeared:
"As of December 29 My Verizon services will no longer be accessible for your device".
It also states that to manage your service, use your computer to access your account or manage it directly from your device.
I don't know if this applies to my account only or the whole system.