I’m a little unsure if it really is an advantage when there are 4 years between two Fairphone models (and IIRC the FP3 was delayed and should have been released earlier ending in a situation where the company had nothing to sell during several months of 2019).
My assumption (but no idea if it holds) would be that people interested in Fairphone would not replace their phone if the next model came out after 2 years.
But on the other hand, personally, I wouldn’t have bought an FP2 early 2019. When people’s phones break and the only option with Fairphone is to buy 3 year old hardware (and not-very-long software support as it is counted from initial release not time of purchase) my fear is that a lot will go for an un-fair device again.