We used to put up a preview for each video that we added each week. We stopped doing that and saw no decrease in sales but a substantial decrease in bandwith usage. We pretty much tagged the same folks that came week after week to watch the previews, snag them and then never join. As long as you offer previews that are a good indication of the scope of your material then I believe it works just fine. We are updating for our members and customers, not for the 'i bet I can get off to this in less than 40 seconds' gang.