These are time-limited rewards that you don't have any reason to sit on. We plan on doing drops every month. Claim them quickly, or come back next month.
If we leave similar time-limited rewards available for longer periods than we plan on doing drops, it's less likely that people will re-engage in the twitch drops as they already have the stuff waiting for them. This sort of behavior is not uncommon (get limited reward, claim it 6 months later when it's more "unique"). This would allow people to sit on their rewards with no intention of engaging with the community, which is kind of the point of doing Twitch drops in the first place. The people who treat it as a way to AFK and get free stuff are going to be a lot more concerned with losing anything, compared to the people that regularly engage in stream activity and would get these rewards if we randomly turned them on without notice.
The point isn't to give you guys free stuff, it's to drive engagement with the people who are spending their free time promoting the game in a positive manner. That's also not to disparage anyone from participating, if you want to essentially viewbot and not engage, that still helps the server gain exposure as high viewer numbers drive new players to the game. However, we intend to keep those viewer numbers high month-to-month, and that means time-limited rewards that you'll need to come back for, and we certainly hope you will.