Whats the logic behind extending battery life when you paid a premium for a laptop with an easily replaceable and reasonably priced battery? Surely the extra time of uae over years is worth more than the replacement cost?

Well, I very rarely take the laptop away from my desk.

If I knew I was going on a long trip, I would put the charge up to 100%.

When I do go on a long trip, then there's benefit in conserving battery life, because the charge I'll take with me will be substantially higher.