Several in-game months later, I was walking down the very same road and -- holy crap! -- it was all still there, in a perfect circle.
In a somewhat similar vein, I dropped a shield outside of the Used Wares shop in Windhelm and it has remained there for months.
This makes me wonder, do you really need a safe chest to store your stuff in? Couldn't you just drop it all in the road somewhere? I don't think those areas respawn like dungeons do. I guess I'm wondering if anyone else has experienced this, or if it's a fluke in my game (or perhaps I reenter the cells enough to keep them from respawning -- though I'm pretty sure I was never on that road to Windhelm in those interim months).