I think that the "Lifetime" that most auto manufacturers refer to is a matter of "to the end of warranty service period." They would prefer that we all buy new cars by the time our old ones reach 100k miles.
ZF makes the Tiptronics that are in the 986s and many other cars. Here is what they have to say:
clipped from their web document:
http://www.zf.com/media/media/document/brands_3/service_information/sitematrix~1/transmission/cars_4/englisch_3/modelluebergreifend_1/ZP_SI_Oelwechselkit_EN.pdf
...and I came across this letter while working on another car brand:
http://blog.********************************************* ***/wp-content/uploads/2012/03/ZF-oil-service-letter1.pdf
Many auto companies have revised their original lifetime service and brought it in line with the ZF recommendation.