I don't think it's the characters. I have two characters and they've never crashed on my stable worlds. My first character, however, have had more than its fair share of crashes on my previous worlds. That's enough for me to write off the characters as a cause of crash. I only said "unstable worlds" because there must be something in the previous worlds that isn't present in my current worlds. Unfortunately, yes, the variables involved is a nightmare. If I could somehow isolate what exactly causes the crash, like a reliably repeatable crash, then that would definitely help. But so far most of the crashes seem to be random. It can happen regardless of biome, of depth/height, of day or night, of proximity to certain things or NPCs... In the end, all I can really say is that my current worlds have never crashed on me when others have. Make of it what you will.
I've read somewhere in this thread, somebody thought it might be similar to the memory leak bug in Vita version? Maybe the game is tracking too many things at one point and gets choked up or something? I don't know... :/