Gavin and @NicolasDorier have a point: If there isn't actually scarcity of NOPs because OP_NOP10 could become <type> OP_EX (if we run out), it makes sense to chose the original unparameterised CLTV version #6124 which also has been better tested. It's cleaner, more readable and results in a slightly smaller script which has also got to be a plus.

On Tue, May 12, 2015 at 8:16 PM, Jorge Timón <jtimon@jtimon.cc> wrote:
This saves us ocodes for later but it's uglier and produces slightly
bigger scripts.
If we're convinced it's worth it, seems like the right way to do it,
and certainly cltv and rclv/op_maturity are related.
But let's not forget that we can always use this same trick with the
last opcode to get 2^64 brand new opcodes.
So I'm not convinced at all on whether we want  #5496 or #6124.
But it would be nice to decide and stop blocking  this.

On Sat, May 9, 2015 at 11:12 AM, Peter Todd <pete@petertodd.org> wrote:
> On Tue, May 05, 2015 at 01:54:33AM +0100, Btc Drak wrote:
>> > That said, if people have strong feelings about this, I would be willing
>> > to make OP_CLTV work as follows:
>> >
>> >     <nLockTime> 1 OP_CLTV
>> >
>> > Where the 1 selects absolute mode, and all others act as OP_NOP's. A
>> > future relative CLTV could then be a future soft-fork implemented as
>> > follows:
>> >
>> >     <relative nLockTime> 2 OP_CLTV
>> >
>> > On the bad side it'd be two or three days of work to rewrite all the
>> > existing tests and example code and update the BIP, and (slightly) gets
>> > us away from the well-tested existing implementation. It also may
>> > complicate the codebase compared to sticking with just doing a Script
>> > v2.0, with the additional execution environment data required for v2.0
>> > scripts cleanly separated out. But all in all, the above isn't too big
>> > of a deal.
>>
>>
>> Adding a parameter to OP_CLTV makes it much more flexible and is the most
>> economic use of precious NOPs.
>> The extra time required is ok and it would be good to make this change to
>> the PR in time for the feature freeze.
>
> Done!
>
> https://github.com/bitcoin/bitcoin/pull/5496#issuecomment-100454263
>
> --
> 'peter'[:-1]@petertodd.org
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