So batteries are actually based on something called charging cycles which is why power saving mode is important to use because it's not power saving, it's battery saving.

Every time you let your phone go from 0% to 100% then back down to 0% that's a full cycle. Most phones are designed to be charged about 10,000 times, from 0% to 100% back down to 0%. That's 10,000 days, that's 27 years.

That's based on continuous, non-cumulative usage of battery life, so in one charge of using it straight and the battery death happens in 3 hours straight and then you charge it again. Which means it's life is lowered by like ⅔'s

Cumulative battery usage is based on day-to-day and that would technically be a cycle. So 50% one day, 20% the next and 30% the final day. That to me doesn't have much of a good explanation on the actual charging cycles that to me is more based on use which does play into battery life.

Idk man, they nerf the software and speed if you have a mainstream phone, like asshole or samesong, so a new battery isn't gonna solve that.

Thinking back to my ngage qd, having a battery cradle was chill but with all the technology we have today, it's stupid to want to keep the same phone for more than 6 years at a time. I think given he economics behind phones people clutch on to them for dear life because of how expensive they are to find just as good if not a better phone than the one that's in your hands, other than that upgrading to after market unlocked phones is still the way.

Edit: Even though it would cost a lot manufacturers can still replace the battery. It's not impossible to get a battery in a sealed phone replaced.