Two batches; roughly the same process; one with poor bind

[LinkMeAllOver]

So, I'm trying to get my head around something that happened today. I made two 30 lbs. pork sausage batches over the last few days. In both cases they were straightforward pork+salt+dried spices/herb recipes with nothing that would mess with the bind. Same cut of pork (shoulder butt), I mixed them the same amount of time in the same meat mixer, dissolved the salt into water for both, everything basically the same. One of them had a perfect bouncy bind, one not so much. I'm baffled. The only difference I can point to is that in the case of the good bind I broke down and ground the meat, then it sat in the fridge for a couple days before I mixed and stuffed, while the one with the poor bind was all done this morning in the course of a couple hours, whole cuts to sausage links.

I have noticed in the past that farce that has sat for a bit (even just overnight) usually sticks to itself a little bit and can be scooped out of the meat lug in huge chunks, while the farce for the sausage today with the poor bind was more loose and crumbly. Does the meat release some of the proteins on its own before salt is introduced? Should I be in the habit of grinding and letting it sit overnight before mixing and stuffing?

This also brings up another question I've been pondering: how long until a bind fully sets up? I know that waiting a couple hours between mixing and stuffing can make the meat harder to work with and result in more air pockets, easier breaking of the casings during stuffing/twisting. But how long after mixing has the bind fully set up to where it won't firm up anymore than it is?