I was a seasonal PT package handler, and was hired as permanent after peak. Yes there was an open spot that I filled. Yes I would think that helping on pre-load would help your chances of being hired.
I've helped a driver that said he was a driver-helper for 3 years before he was hired on, and he is now about to retire.
The fact that this is your 2nd year driver-helping makes me assume that you are reliable and eager to work, I wouldn't think they'd call you back if you were not. That's my advice, to not miss any days. Let the pre-load sup know that you are there to work and ask him/her if there is a chance that you'd be hired after peak. I've read some posts by upstate about how he got his helper a job after peak, If you are with the same driver often, mention this to them and maybe they will give a good word for you. Good luck and I hope you get hired.