If I went to a nursery, bought a plant, planted it and 30 days later it died I would have no recourse.

A lot of places have a refund if it dies policy. As I can kill off the most robust of plants I have never had the nerve to take one back and display my ineptitude for all to see.

As items have to be returned in the same condition as received and they waited 30 days and sent back a deader they would not have complied.

I think this comes under the heading of worrying about something that is hardly likely to happen, the buyer would have to return by trackable post, probably cost nearly ten bucks for most of your items, to get back not much more.