Question about Held packages at Customs or Local Post Offices

If an item is held at customs, and nobody comes to claim it or give clearance info, then:

a) how long in general do customs hold it for?
b) after that time expires, do they return ship it back to the sender or just chuck it away in the trash (etc)?

If a post office has your package and nobody comes to claim it/pick it up, then:

a) same as above
b) same as above


I realize it may differ from country to country, but in general, is it usually automatically returned to the original shipper or just "abandoned"?

I know the post office in the UK hold your packet for 18 days, unless its a special delivery. Thats calendar days not working days.

the time range they hold if for ranges from a couple days to a max of about 3 weeks or so, then they ship it back to sender

I think they are definitely sent back to sender, if nobody claims it. That is true for most countries.

Yes, it would be nice if they do send it back, but how would we know? Does customs/post offices have a tracking number when they return ship something that wasn't claimed/picked up? How can I track that they are sending something back?

Actually, I have thought about just tracking down that country's customs number and or even
that buyer's local post office and just calling them myself to ask if they have anything being held.

Do any of u guys go that far to call your buyer's local post offices all the way in Kuwait or Israel
or Germany? I'm going to do that now. It'll cost me money for calling long distance but if there's
no other way to communicate, then I'll call them myself.