Agree with the longevity of the contacts...typically they'll outlast your panel. As far as a junction point goes, rules of thumb, make sure it's big enough for the cablesand enough slack for service. with splices and remains accessable. In your case, I'd just gut the DSC can and use that....plenty big and no purchase/modification needed.
Solder and shrink is an option, but many people tend to create cold solder joints or overheat the conductors/insulation, which adds to the service woes. Punchdowns would also not be a choice in my book. Extra work for no reward or ease of use.
+1million on the gel filled B-connectors. Strip, twist and properly crimp (not overcrimp or flatten) using a tool designed for insulated terminals, since most don't own the real tool to press them, and you're good. Actually, back in the day, Bell labs (inventors) stated that properly spliced conductors in B-connnectors are electrically equivalent to a solder joint.
