Isn't when Luke is lying freezing to death in a pile of snow a with multiple Wampa injuries kind of an awkward moment to appear to your former apprentice and tell him that he has to go to the Dagobah system? Now you could argue, "Hey, maybe Ben has no control over when he can Force Ghost appear" but I can shenanigans on that one since Ben has appeared at incredibly convenient times before and after that ("Blow up the Death Star, Luke!" "Hey, Yoda, let poor Luke learn to be a Jedi!" "Here's that lie that I told you about Anakin Skywalker..."). Now, movie-wise, it works great - is this Luke dying and going crazy in his final moments? That makes sense. But, geez, Ben why would you tell Luke to go to the Dagobah system after he's been almost eaten alive? Can't you appear while Luke is having a hot coca or when he's changing power converters on his X-Wing or just before he ducks out to use the bathroom or something? It's not as if Luke needed to be bossed around and giving a travel plans while he's lying halfway to death in Hoth's snowfield? Besides, Han showed up literally seconds later!