I try to work off the best available information on a subject, stuff like this link on oil shelf life helps.
http://www.machinerylubrication.com/...t-storage-life
Tables 3-6 show what oil companies recommend. The recommendations do vary though.
They changed the TCW oil spec's because a better formula was needed even for the old motors, the lubrication needs of a carb'd 2 stroke outboard didn't change much from the mid 60's to recent years when carb'd 2 strokes went away, they just made the oils better, this resulted in cleaner burning and better lubrication.
Changes that did take place were the elimination of leaded fuel, it acted like a lubricant, plus E-10, old recommendations (oil spec's) didn't take these into account. Your old motor is now running on different fuel than it did a couple decades ago.
You could probably run most any carb’d 2 stroke on 30W motor oil and it would run OK, might smoke more, build up more carbon, plus a few other things, but it’s not like you would see an immediate failure and say it was the oil.
I see many posts on this site promoting the benefits of a good decarb periodically, and the potential issues if carbon does build up. The new oils are formulated to help prevent carbon build up, the old formulas did this less well.
People frequently confuse the base oil with the finished product, the base oil may have no real shelf life, the additive package is what can degrade over time.