I have a mustang pfd that is a few years past the expiration of the bobbin needing replaced. Someone correct me if I am wrong, but I think it is made to simply dissolve once it gets wet and then the inflation is triggered. So, am I correct in thinking that as long as I am OK with the possibility of it accidentally inflating due to an old bobbin then I am fine not replacing it immediately? The risk is not that it wont work or inflate at all. Right? It’s still armed and never gone off.

would you bet someones life on it...?

Based on my understanding of the mechanism at the moment - yes (and it would be me I’m the only one wearing it)
But I am wondering if I am wrong. The mustang website simply says replace after 3 yrs to avoid inadvertent inflation.

if you were checked by the game warden,..you might get a warning, maybe a ticket. for expired life jacket..

No I carry both type 1 and type 3 on the boat as well as a float cushion - no issue there.

My experience with this is that the material that is made into the bobbin starts to break down and becomes weak.
So while it is still in tact but expired, the humidity in the boat or while wearing it in the rain could simply set it off.

What I do is carry the expired bobbin in a ziploc. This way in the event I had fallen in, I could re-arm my vest with one of the old bobbins.