To be honest I prefer to use a power bank, it’s more convenient than having to swap batteries (i used to do that too) as you don’t have to power down the device. And one power bank can power many different devices, so i don’t have to buy a new one when i Change phones, and can use the same power bank to charge my earbuds, kindle, smartphone, and a variety of other devices, or lend it to someone.
Having said that, i did have my Nexus 6P battery degrade and had to be RMAd, lucky for me it was within warranty. Battery is the fastest failing component so being replaceable will go a long way in prolonging devices lifetime, but doesn’t have to be user-replaceable.