Looking at the bundles and the co-op bundles some of them have ending dates of many years. It feels to me that offering a bundle should be for a maximum of, maybe, a month. Or certainly less than a year. Isn't the point that it is a limited time offer?

I don't think bundles should need to have an ending date at all.  Bundles can be used as sales events, but they can also be used for setting a regular price for purchasing multiple products together.