I'm familiar with the use of solder on PCBs from dealing with them in a manufacturing facility for 30 years, from the good old days of point to point wiring, to hand stuffing/soldering PCBs and lead free SMT with all the RoHas male bovine meadow muffins that goes along with it. I'm also aware of the wire breaking before the solder joint, especially solid wire or the portion of stranded that gets tinned when the joint is made.

I've seen the aftermath of 72 hour shaker table testing and had to deal with the result. Early lead free solder and SMT easily comes to mind. :scowl:
I think the context of the OP was more toward home repair of the average type of connections found in guitars. Screw and crimp connectors in this context are bulky and inconvenient. Although properly made crimp and screw connectors can seal a connection from the atmosphere, heatshrink
will not keep oxygen from a mechanical connection. Over tightened screw or crimp connections will weaken the lead(s) being connected and will most likely cause failure in any device subject to vibration due to lead breakage unless the leads are firmly supported outside the connector.
Do-it-yourselfer repair/modification of PCBs of any technology as used in guitars are relatively few and far between. Personally the few thousandths of an Ohm added by a few mills of this Glue, if used for a few average connections in a guitar or any other low current application, other than RF, wouldn't bother me at all, but I would not use it for dozens of connections. It's kind of like stacking gnat's hairs. If you stack a few it still doesn't add up to anything significant. I would still want a good mechanical connection for anything with a lead or that had significant weight. Due to the cure time the connection would also need to be stable to prevent it from pulling apart due to any stress caused by twisted leads, gravity, poking at it to see if it's dry, etc.