Just a quick tip from someone that is currently working on Loremaster and does a lot of old instance runs where mounting is not possible: If you have a run speed buff that has a cooldown and limited duration you can disconnect (turn off wifi or pull your ethernet cable) right before the buff expires and still retain the same run speed. While disconnected you will aggro any enemies that you run through, will be vulnerable to attack and will be kicked if you do not periodically reconnect (reactivate wifi or plug in your cable) to refresh the buff, but can clear instances a good bit faster.
Just one example that I timed was my run speed from Majordomo to Ragnoros in Molten Core. I ran the length of the instance in two minutes using my priest's Angelic Feather on cooldown but was able to cut that time 25% to 1.5 minutes by disconnecting after I got my speed buff and refreshing it once halfway to Rag. This method can be used to run back faster after raid wipes, clear old instances faster, and run through long indoor dungeons where there is no real danger of being killed. The time saved from each DC isn't that huge but you can save a lot of time over many uses of this method to maintain your run speed buff.