I’m not particularly against soldering, but it really isn’t required if you have a proper crimp. It’s an extra step which does not provide much benefit.
With a proper crimp, it creates a cold weld and the solder shouldn’t even flow into the other end of the lug. Soldering the ends may make the connection brittle and eventually cause a failure if in an environment where it is allowed to move / flex without additional strain relief.
If you want additional corrosion protection, pack it with a dielectric before applying heat shrink. I do recommend buying adhesive linked shrink with does an excellent job of keeping moisture, dirt, debris out.