Luckily user replaceable batteries are coming with an EU regulation some time within the next 5 years, but so far fairphone is the most repairable phone you can have. I don't think you can replace mobo or chipset, but it does allow replacing quite a few things. For me the 3 most important ones are battery, charging port and screen, as those are the most likely for me to get worn out or broken. I haven't bought it yet because my current phone is still somewhat chugging along, but my next phone will definitely be a fairphone.