When soldering them I use minimum heat plus I use a heat sink (contact area) and I test pressure on each contact afterwards that's why they take a while to make
I do not solder like you would normally do ie feeding solder in I cut exact 2mm lengths of very small diameter solder so as soon as you touch with fine pointed iron set to lowest heat. After all the leads made my plugs have exactly the same grip as before soldering

I know which lead I would rather use .....

Alan