Advertisements We really have gotten a lot of good use out of the ability to use Comcast's On Demand service on our TiVo Roamio. We have HBO and really appreciate having been able to effectively catch up with years of their original series that we've missed. What I'm wondering is whether Comcast imposes any limitations on adding and removing premium services. We're in the middle of a two year contract, and I don't want any aspect of that affected. Presumably, we'd pay full price for adding the extra service (Showtime) but eventually (after we worked our way through the 100+ hours of original programming that we haven't seen) we'd not seem much point in keeping it and would want to cancel.