I have made four characters in the last month or so and on all my recent playthroughs my Blacksmith has dissapeared. However, on a character I just made Ed persisted throughout my entire story. The only thing different from this playthrough is that I didn't suicide in 2-1 to bring my world tendency down to pure black for the primevil demon there. On all my other characters I suicided in 2-1 after releasing Ed. When I went back to the nexus, then came back to 2-1 to suicide again, sometime Ed wouldn't be there. So… it looks like if you have a problem with Ed dissapearing then don't suicide in 2-1.
Hope this helps.