A tale of battery cables
Do you honestly think solder makes enough of a difference to be that picky about? I wouldn't think it would much to worry over........but then my knowledge of things electrical is lacking. Among other things.
I guess it depends on many factors. I have found in 45+ years of soldering wires, that with vibration and age they fail just past the solder.
I also know a good mechanical connection must first be made prior to soldering. The concept of pellet soldering a lug seems flawed, because the connection must be loose to get the cable inserted. The solder is about 10 times less conductive than copper, so compared to a crimp the conductivity is less.
If the connection is properly crimped, then soldered, solder leaches in at an atomic level, again resulting in less conductivity. The heat during soldering aneals the copper where it cools quickly, and hardens where it cools slowly. Copper easily work hardens, so breakage often happens close to joint.
I am also familiar with what can happen with loose soldered joints with high currents, solder vaporizes. This can happen in fractions of a second. I have verified this many times in lab tests related to product development.
I don't worry about it. While my newly terminated old cables may last another 35 years, that is well beyond my estimated lifespan.
