If its stock then its fine. That system worked for 100 of thousands of cars. Add a relay circuit for the headlights. Why? because the original lamps were rated 40/40 Watt. Since the 70s replacements draw more. Bonus of using a relay harness is that reduces the maximum possible load through the R6 wire by 9 amps. I'd say the biggest issues are condition of wires and connectors. That most certainly includes the quality of the repair and replacement work. It also includes good wire routing and support. I, like many others, didn't give those last two much respect as young shade tree mechanic. But thats a big part of why wires and junctions survive long use without damage.
If you really want to do some reworking, again assuming stock loads, then copy one of the 'fleet' or 'heavy duty' wiring schemes. A parallel wiring is another approach, which is similar to the 'heavy duty' scheme used on 70s models with rear window defrost grid.
The voltmeter in the cigar lighter is OK for an occassional check. Check your year for where in the fusebox that is wired to. ;)
Sure don't want a slow drain! Thats exactly the type of thing that causes high battery draw and damages stuff!
