In my org-mode setup, initially I used to preview the whole buffer all the time. However, as my files grew bigger the waiting time for this has become prohibitively expensive. Since then I have set it up to continuously recompile the file in the background each time the file is saved. It works pretty well since instead of spawning a new async process on each save, I have a single background process which recomiles in sync and thus needs not reload all the emacs on each recompile....