Render stopping without any reason

Hi everyone, I've been struggling with rendering for years now.
My projects are often 15~20 minutes long with mainly AE dynamic link sequeces. The AE files only has keylights, vectors and some keyframes, no other heavy effects.
More often than not in regards to big projects the render will get halted while the expected render time keeps going up, forcing me to requeue it. 
What's more confusing is that sometimes after requeing it will render smoothly without any problem.
Has anyone encouter the same issue? and how can you fix this? I've missed so many deadlines because of it.