"I'm feeling pretty confident my phone will last me another year"
That's great to hear. I used to be one of those people who got every new iPhone release (or at most every 2nd release), but I've been keeping my trusty old iPhone 6 going for a couple of years now and I have very little interest in getting a new phone any time soon. My 6 is getting a bit slow, so if performance is better on iOS 12 that's great news
Literally same situation here except with a 6 Plus. Upgraded this morning and the speedup and faster animations are pretty damn noticeable. Camera used to sometimes take 6-7 seconds to open which is now cut to about 1-2s. Definitely recommend the update, the new features are also pretty convenient, I especially like the new Do Not Disturb and Screentime provides some interesting stats. Now it's just battery life getting awful, but I've been putting off getting the battery replaced because spending a week+ without a smartphone is borderline impossible and I have no backup device.
Your old battery might be causing your slowness. Replace it for $30 in the store, too; you don’t have to be without it for more than an hour if they have the parts in stock. My iPhone 6a is super quick. Camera opens in under a second.
I'm on a 6+, and the performance is a significant step up (more so than going from a degraded battery to a new battery sometime after the iOS 11 thing). It wedges me somewhat between a rock and a hard place; I'm getting the grey bar of death (https://ifixit.org/blog/8309/iphone-6-plus-gray-flicker-touc...), so really want to replace the phone... but the performance is back to where I wouldn't otherwise bother. Bugger.
That's great to hear. I used to be one of those people who got every new iPhone release (or at most every 2nd release), but I've been keeping my trusty old iPhone 6 going for a couple of years now and I have very little interest in getting a new phone any time soon. My 6 is getting a bit slow, so if performance is better on iOS 12 that's great news