It is true one can continue to improve the stability of OLED just like LCD 35 years ago. However, one should realize that what can be improved are the extrinsic aspects, such as passivation, defect reduction, etc., and the intrinsic aspect, the strength of the chemical bonding, is hard to change for certain types of materials. Likely, as in biology, difference species seem to have different lifespans. It is probably hard to make a dog last as long as a human. So could an OLED ever last as long as a LED under the same conditions? Maybe at low intensity applications the difference is not practically important.
To assessing the long-term stability of OLED materials, one should come up with a reliable accelerated aging technique instead of waiting for 35 years while trying to get incremental improvement.