Oh yes, plug life. I think the main difference between then and now is the quality of the plugs used. The 100,000 mile plus plugs have platinum electrodes and they just plain last longer. The main problem today seems to be getting them out of the heads without damage to the head or plug when replacement finally becomes due. Especially in some Ford V8 engines .... though some of those plugs are ejected by themselves but that is another issue.

We had quite a few fleet vehicles where I once worked and with the advent of coil per plug or similar, ignition problems were really a thing of the past. After a few plug replacements that resulted in head damage, we pretty much got to the point of leaving them alone (unchanged) unless there was a definite plug related issue. I'm sure we retired quite a few vehicles with close to 200,000 miles on them that still had the original plugs and they were still going strong. I've seen some plugs at 100,000 that really looked very good.

Regarding multi-spark, I believe some newer passenger vehicles now use that to increase efficiency. I believe the Chrysler hemi is one of them ...... two plugs per cylinder with multi-spark. IIRC, I think I read that in their advertising literature some time back. Someone may have to put me straight on that one though..... getting older ya know! At any rate, I don't believe that multi spark would be an issue with modern plugs, conventional or platinum.