another feature that could be useful is having some kidn of permanent bundles, like what happens on Steam (for example a collection of games of the same series with a small discount). Probably you can do it with the normal sales bundles but you need to set the expiration date to like 5 years from now and looks a bit weird :)

I think this is a good idea, we'd like to add something like this sometime in the future. In the meantime, setting a long duration is the only way to accomplish it.