The need to exempt various types of traffic for business reasons is ultimately why I think monthly data caps will fade away for cable/telco-provided Internet service.

An example would be some provider like Disney saying that in order for Comcast (or some smaller operator) to be able to carry their TV channels they must also zero-rate streaming from their sites. Or Hulu and Verizon do a deal in which Hulu content doesn't count toward a cap on Verizon phones. These things are becoming more common, and I think the difficulty of figuring out which bits count and which ones don't (especially when they all come from the same CDNs) will prove to be more trouble than it's worth.

Exede seems to be moving away from this model, actually. Their new plans don't offer unlimited periods at all, but instead, some types of traffic are exempt from the caps. The problem with that is Exede won't say exactly what type of data is exempt other than "basic web browsing and email." No one really knows if that includes HTTPS, HTTP2, QUIC, WebSockets, etc.

My home town's ISP (http://pris.ca) does this for its wireless customers. Transfer between midnight and 7AM doesn't count towards your 10GB/mo cap.

Lots of Australian ISPs use this model. For example: TPG Broadband Off-Net 50GB -> 10GB peak / 40GB off peak (2am-8am)