The video revealed that there is a lot of corrosion going on with one of the lines (I have three independent lines) coming out of the house that merged after the driveway into the main cleanout). It has a lot of buildup and scales and the shape of the pipe from the inside is no longer circular but more like the inside of a "cave".
One option is to find a way to "rim" out the corroded portions (if it's even possible). The other option suggested by the plumber is to lay a new PVC pipe. This would involve cutting a 72 feet long 8" wide trench along my 4" concrete slab, plus a few laterals to tie in from the three bath, each of those would vary from 4 feet to 8 feet in length. Obviously this is a drastic approach and the most costly approach.
My question is, what is the life expectancy of a cast iron pipe? 25 years? 50 years? 100 years? Mine has been in the ground since 1972 in the hot and humid Miami weather with a high water table, near the ocean so water may have salt.
It is "normal" cast iron pipe (SV) and not XH if that helps.