Teleport can go wrong even when you are very familiar with the destination, but if you have an associated object, you can arrive at the right destination with 100% certainty.
The spell describes an associated object as follows:
"Associated object" means that you possess an object taken from the desired destination within the last six months, such as a book from a wizard's library, bed linen from a royal suite, or a chunk of marble from a lich's secret tomb.
But what does taken from the desired destination imply about how long the object must have been there, if anything?
Technically, everything the wizard has on their person has been in any location they visited in the last six months, and hence has been taken from there. Does this mean the wizard, as long as they do not change their clothes, shoes, spellbook or whatever object they carry with them, can safely teleport to any place they visited in the last six months? Does it mean if the wizard receives a letter from the king, he can teleport to wherever that letter was written? If not, what can reasonable criteria be?
It's clear from the examples, that the object does not need to originally be from the destination. The bed linens were certainly manufactured somewhere else and then transported to the royal suite, and they might be changed daily.
Obviously, the DM can make a ruling on this, but is that all? What are your experiences with ruling on this, and how well did these rulings work?