I have seen tinning cause problems. The connection gets hot and the solder reaches a plastic state and relieves the tension from the screw, causing a bad connection. And bad connection means more heat, more heat means more solder being deformed and so on.
I also have soldered for a bit over half a century.
When I started the electrician I worked for soldered all connections and then placed diapers on them, teaching me to do the same. For you younger persons who don't know what that is, a "diaper" is made of flexible rubber, has what looks like a small pot with handle.......... "handle" extends out forming a ring. The "pot" part is placed over the twisted and soldered wire ends, the handle part goes up over and between the connected wires and the ring part is stretched out over the diaper (pot).
I moved from the area where I did the wiring in the homes built in 1962 using that technique.
About ten years ago I came across an old house which was wire connected in the same manner in southern California. I was replacing fixtures and in most of those the solder had disintegrated which allowed resistance, wires had heated causing the insulation to either fall off or become so brittle they had to be repaired.
At any rate, I noticed the deterioration of the solder joints in the ones in calif and wondered if the same happened those I did.
Until I saw that, I still believed soldered joints were better, but now my belief is in twisted connections, good wire nuts, and if in damp areas using an electrical dielectric grease in them.
