Hello Harry,
I think Stephanie's solution makes a lot of sense. Our policy is actually not to hold anything pending the decision to collect and until recently we were very strict about it. If someone brings us something in person, we take pictures and capture info but don't keep the item(s) pending collections committee and board review. If the person is genuinely making the offer in good faith and not just trying to get rid of stuff, we find they are usually happy to comply with our policy, and pleased that we are so conscientious about our collecting. When someone is trying to "dump and run" and says "well I'm just going to throw it away if you don't take it right now" we say "we understand and that's your choice." This almost always calls their bluff as realistically very few people need to get rid of their item(s) right this second (and if they truly care so little about the historic value that they'll throw it away rather than be slightly inconvenienced, it's unlikely to be so mission critical to our collection that we missed out by sticking to our guns).
I put this policy in place because our previous temporary custody receipt did not have a deadline for retrieval like Stephanie's does, and I worked in an institution with the same that had chronic non-retrieval of items which got left in legal limbo, taking up valuable space. However, we have now relaxed a bit and allow temporary custody when a donor genuinely can't keep the item(s) until review (they are from out of town or are moving, etc.), but we don't offer retrieval as an option, only the agreement that we can dispose of the items if we don't want them. A retrieval deadline might be something we could build in in the future if we want to dedicate a space to store things pending review.
I also agree with Stephanie's assessment about emotional burden, and having hoarding tendencies myself, I can understand it (for me, I think it comes from a root indecisiveness that is alleviated in a museum setting because there are established criteria for what we keep and it's not just my subjective choice). As American society wrestles with our unhealthy relationship with stuff (see https://www.activecollections.org/), I think museums could lean into being that mental heath aid for our communities. It's definitely an extra burden on us, and while my own institution is still working through a massive culling of our own mission-irrelevant martials, we're not ready to take it on yet, but perhaps in the future.
Good luck with whatever you decide to implement and thank you for the discussion prompt!
Michelle Nash
Curator of Collections
Elkhart County Historical Museum