Replace by fee is the better approach.  It will ultimately replace zombie transactions (due to insufficient fee) with potentially much higher fees as the feature takes hold in wallets throughout the network, and fee competition increases.  However, this does not fix the problem of low tps.  In fact, as blocks fill it could make the problem worse.  This feature means more transactions after all.  So I would expect huge fee spikes, or a return to zombie transactions if fee caps are implemented by wallets.

-Raystonn

On 8 May 2015 1:55 pm, Mark Friedenbach <mark@friedenbach.org> wrote:
The problems with that are larger than time being unreliable. It is no longer reorg-safe as transactions can expire in the course of a reorg and any transaction built on the now expired transaction is invalidated.

On Fri, May 8, 2015 at 1:51 PM, Raystonn <raystonn@hotmail.com> wrote:
Replace by fee is what I was referencing.  End-users interpret the old transaction as expired.  Hence the nomenclature.  An alternative is a new feature that operates in the reverse of time lock, expiring a transaction after a specific time.  But time is a bit unreliable in the blockchain