Taking a second look at OP_EXPIRE

The concept of Miner Extractable Value (MEV) introduces a unique dynamic within the cryptocurrency ecosystem, particularly concerning transaction expirations and the implications for coin supply and value. The phenomenon occurs when a transaction that has the potential to expire is not mined, leading to the unspent funds being effectively burned. This scenario benefits the entire network as lost coins equate to a donation to all holders; reducing the supply can lead to a proportional increase in the value of the remaining coins. This is especially relevant as block rewards decrease and eventually hit zero, prompting a shift where only pre-existing coins are in circulation. At this juncture, entities holding large amounts of cryptocurrency ("whales") might find it advantageous to encourage behaviors that lead to more coins being burned, enhancing the value of their holdings.

Given the relatively centralized nature of mining operations due to the limited number of pools, transaction censorship becomes a viable strategy for influencing the scarcity of coins. For instance, if a transaction is censored by the majority but included by miners with a 1% hashrate, it faces a high likelihood of expiring after 100 blocks if it cannot secure confirmation within this window. The upcoming activation of new rules could exacerbate this issue by providing an incentive for pools to censor transactions with timelocks shorter than 100 blocks, knowing they cannot be added later once expired.

One proposed solution to circumvent the need for consensus changes while addressing transaction expiration involves confirming an alternative version of the same transaction. This approach would automatically invalidate all other versions that utilize the same inputs, thereby streamlining the process without necessitating modifications to the underlying consensus mechanism.