I disagree with the importance of this concern and old soft/hardforks will replace this activation mechanism with height, so that's an argument in favor of using the height from the start. This is "being discussed" in a thread branched from bip99's discussion.
Anyway, is this proposing to use the block time or the median block time?
For some hardforks/softforks the block time complicates the implementation (ie in acceptToMemoryPool) as discussed in the mentioned thread.
Jorge Timón via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> writes:
> I agree on using height vs time. Rusty, what do you mean by being easier
> for bip writers? How is writing "block x" any harder than writing "date y".
Three years from drafting is reasonable. How many blocks is that? Hmm,
better make it 6 years of blocks just in case we have a hash race.
Deployment speed is measured in months, not blocks. It's hard enough to
guess without adding another variable.
Cheers,
Rusty.