Input-triggered transaction expiry

In a recent discussion, there was clarification and expansion on the concept of input expiry in blockchain transactions. Initially thought to apply primarily to scenarios involving double transactions, where two transactions are planned sequentially, it's evident that the implications extend beyond this specific case. The motivation for introducing input expiry stems from the need to discourage certain behaviors among miners, such as reorganizations (reorgs) that can destabilize the chain tip, especially significant in environments where block rewards have diminished or subsidies no longer exist.

The principle behind input expiry is to introduce a mechanism where dependencies in transaction confirmations can have financial implications for miners. By setting an expiry on inputs based on their confirmation time, miners might incur losses if they delay confirmations strategically. This approach aims not just to mitigate undue advantages gained through reorgs but also to enhance overall stability within the blockchain network by ensuring more predictable and timely transaction confirmations.

This conceptual shift suggests broader applicability for input expiry than initially considered. It could serve as a standard practice to encourage more disciplined and less manipulative behaviors in blockchain operations, potentially leading to more robust network integrity. Such measures would be particularly crucial as the ecosystem evolves towards a post-subsidy model, where traditional incentives like mining rewards are reduced or phased out.