There’s a big spectrum of behavior here, from the weekend tinkerers who are overambitious but have no trouble getting rid of stuff once they realize projects are DOA to the compulsive hoarders who can’t help but choose stuff over virtually everything else in life (including relationships). Does he buy a ton of stuff as well? Accumulate so much that your movement in the house is impeded? Have an inordinate amount of trouble parting with objects? If your husband’s curb habit does not seem connected to more serious psychological underpinnings, then you can both develop some ground rules. Maybe when one thing comes in, one thing must come out, or if something isn’t completed in four weeks’ time, it goes back out. If the accumulation seems a more intractable problem, he could benefit from cognitive-behavioral therapy.
I can’t tell how much you’ve really talked about this. Not just a rushed conversation about the awfulness of Bouquetgate, but a patient discussion that longtime friendships between two adult women deserve. Sometimes wedding planning (and pregnancy) are stressful enough to cause someone to act out of line with who they really are. Other times, big, stressful events merely bring out who people really are. My vote is to give her the benefit of the doubt and keep trying to work it out. Choose a relaxed and private time on neutral turf to get started.