The reason it works well until 8 am is because you are drawing from your Bonus Bytes allotment.
You draw from your Anytime Bytes from 8 am to 2 am local
You draw from your Bonus Bytes from 2 am to 8 am local
If you have purchased any Tokens, your will draw from your Token Bytes in the event you run out of Anytime Bytes
If your plan has the SmartBrowse feature and you run out of Anytime data and have no Token Bytes, you will not be throttled as long as your data usage rate remains low ... that is no videos, no file downloads.