Question: I was riding Shadowmere near Alftand and I accidentally fell into that canyon near the abandoned tower. The fall was enough to kill Shadowmere. 

I have done a lot of quests and other things such as fast travel, waiting, and sleeping so I am wondering if that interrupted his respawn. Also if I come back to that point before he respawns, is that bad? 

Can Shadowmere just go away and never come back after his death?

I tried waiting in-game for 11 days in Solitude and then returning to Shadowmere's death point, but it did not work. 

I do not want to use script commands because I consider that 'cheating' and I don't want to cheat.

Answer: 
According to the wiki, you should wait [15-20 days](http://www.uesp.net/wiki/Skyrim:Shadowmere) for Shadowmere to respawn at the place he died.
This wiki article claims:

> 
> If Shadowmere is killed, waiting in a main city for 10 days then
>  returning to where he died should respawn him on both PC and console
>  versions.
> 
> 
> 

source: <http://elderscrolls.wikia.com/wiki/Shadowmere_(Skyrim)>