Having spent a bunch of time measuring battery interconnections, here is some perspective:
A mediocre battery connection is maybe .5 milli-ohms. At 200A that generates I^2R = P = 200^2 X .5 X 10^(-3) = 20W So if there were three of these splices in a box that would be like having a light bulb in there - it would get warm
A good connection is 1/10 of that, maybe 50 micro-ohms. At 200A, that generates 200^2 X 50 X 10^(-6) = 2W, or 6 watts for three splices. You wouldn't even notice it.
If the box contains no splices, but has a 4 foot loop of wire in it, then:
resistande of 3/0 is about .08 ohms/1000, or 80 micro-ohms/foot. Again at 200A, that generates 200^2 X 80 X 10^(-6) = 3.2W/ft. So for 3 - 4ft loops at 200A, the power is about 10W.
I've never measured the resistance of a splice, but is highly suspect 3/0 splice made up in a properly made split bolt is as good as a polaris, is maybe not as good as a butt crimp, but still better than 50 micro-ohms.
I don't even thnk you would ever see them - even after twenty years.
PS Would someone mind checking my math - I've been known to slip a decimal or two.
cf