Flour is many years expired but still looks good I have a bag of flour in my pantry that expired 3 years ago, but it looks and smells perfectly fine. Is it still safe to eat?

EDIT: To clarify, today is July 3rd, 2018, and the flour best before date is "2015 SE 04"

Question is different from other existing questions on the topic because the duration of time passed is more extreme (other questions describe a few months).
I am using flour that expired in 2018. I had to use some of my emergency flour due to the corona virus shortages. Its pretty good but not as good as fresh. Id say 90% as good tasting. Yeast on the other hand is different. Ive had a one pound block of yeast in the freezer since 2014 and it still works. Not very well but it works. I have to double up the amount and wait twice as long so the bread tastes very yeasty but it is good to know it can last this long.