Mean kuwait need to replace it with China fighter??

I don't know much about weapon tech, but 30 to 35 years old tech is like getting the best Jap zero fighter of ww2 planes in 1980 (vs 1945) and expect these fighters to be effective.

Some more tech advancement has been accelerating right?

Ops... Incidentally the first version F18 came out in 1970s. If zeroes can be effective vs F18, who knows....

Then again, there are still firms that uses Windows 95 today.
So, I guess tech can last for quite some time.

if PLA initiate war , all the US made jets  can not survive for long . stealth or not. it makes no difference.

These would be the planes that get completely bombed to smithereens before the war starts. Buying 2nd hand seems like good strategy.

Also get more unmanned vtol drones that we can hide in submarines. Those would be the one to take out the opposing Alien forces mothership.