This is one of those questions that we never get an exact answer on officially. Every time the videos are brought up we are told, "The gem videos are a promotional feature and as such are subject to change at random.' Maybe not those precise words but that's the general gist of it -- it's random who does and doesn't get the videos, when they get them and how long they have. Really, all we have is anecdotal evidence on the subject.
For instance, I've never had them offered in either RS or BS in all the years I've played not once. But I have always and consistently had them in DS and CS despite purchasing gems in both of those games so in my case it's a moot point. On the other hand, as gordieprogman pointed out, lots of players swear up and down that they stopped receiving them as soon as they bought gems. I suppose you'll just have to weigh the pros and cons and decide if you do purchase gems and lose the videos, is that going to impact your game negatively enough to discourage the purchase or is it something you can live with.
Sorry there's no definitive yes or no answer for you but such is the way of the ever mysterious s8. Here's a thread dedicated to the subject where you can read other players experiences and thoughts on the issue: https://forums.storm8.com/showthread...ily-gem-videos