As title, i have a transaction un-confirmed since 14/12/2017. I would have thought it should have dropped from the mempools by now?
Thanks in advance for any input you might have
With most default settings, yes. The problem is that it can be re-broadcasted. If someone (like a Bitcoin Cash supporter) wanted to play up the perception of congestion and high fees on the Bitcoin network, they could continually re-broadcast all unconfirmed low-fee transactions. A script can do this trivially. I believe this is why people are commonly having low-fee transactions stuck for weeks at a time now.
From what I've read (sources:
this and
this) the latest additions change the max from 72h to 14 days(!) until a tx is dropped from the mempool.
Also if your wallet or somebody may have re-broadcasted your tx, in a hope to accelerate it. (some "accelerators" seem to only re-broadcast, nothing else).
So if the tx is being broadcast constantly with the low fees it was sent at, it could technically stay unconfirmed forever?
Yes. As long as the transaction is valid, anybody can just keep broadcasting it. There are tools
like doublespend.py that can easily double-spend low fee transactions. You could also import the keys into another wallet and re-spend the inputs.