On my previous 5 years old phone the OLED looks as good as it did when it was new.

My LG OLED TV of 4 years looks as good as it did when new.

I had a PS Vita for about 4 years and the OLED was good as new when I sold it.

I’m not questioning your experience but OLED can last a lot longer than 1-3 years if it’s of good quality and the software has features to help preserve the pixels.