2018 Model 3 - Hardware Upgrade?

I have a 2018 M3 AWD/LR that I purchased new. I absolutely love the car and only have 33k miles on it. Unfortunately due to the old hardware I've never been able to use FSD. I've also been kind of wanting a newer model year but trade in doesn't make sense financially since id have to pay a good chunk out of pocket. Does it make sense to just keep my current 2018 long term and pay Tesla for the HW3 upgrade? If I want to do FSD monthly subscription, has anyone bad luck with Tesla covering the hardware upgrade for free? For others that have gone from a 2018 to a newer model, is there much of a difference in other areas? Thanks