As far as the eCVT fluid is concerned, there are no combustion products that can get into it and contaminate it and there are no clutches or bands or valves in it to produce wear particles. It would probably last forever. Oil doesn't wear out if it isn't over heated. Don't worry about the ICE air filter, if there even is one. If it got so clogged that it restricted flow I believe it would notify you.
I used to think the same thing, (regarding eCVT fluid lasts forever). I know there is no combustion process, bands or valves.
However, consider the following:
1) Do you account for the condensation process, in going from summer to winter and back?
2) Do you really believe that the fluid will be identical 7 years later, in composition to what it was, coming from the factory?
3) I wandered over to the Prius forum. (It has the same eCVT design as what we have). Some of the owners have submitted their eCVT fluid for oil analysis. The results
have swayed them over to changing out their "lifetime fluid" as well. Google "Prius eCVT maintenance".
4) I have not priced out a new eCVT transmission in our cars yet. Someone at the Prius forum got a $6,000 quote. Maybe you have deeper pockets than I, to run that
risk (that your transmission will last a lifetime maintenance free). As for me, I'll pay the $80 + Mercon LV fluid cost, to change it out, every 50,000 miles, after the initial,
100,000 mile change (I thank you very much).