A while ago, I've decided to use an iPhone 3GS on iPhoneOS 3.1.3 as my main phone for a week. A bit more context: My main daily driver is an iPhone 5 on iOS 6.1.4, it's a pretty great phone, has 64GB storage which is gigantic for a phone running iOS 6. I specifically chose a phone I own with handicapped Wi-Fi, and an older OS, so my attention span wasn't quite as broken. The battery on the 3GS had 85% battery health.
Additionally to thinking that using iPhoneOS 3 for a week was a good idea, I also went further and forbid myself from using any hardware or software made after May 2010. For that I used my 2009 MacBook Pro on Mac OS X Snow Leopard, and my 2009 27 inch iMac.
I started out the day by transferring my iTunes media library to my old mac, plugging in my SIM card to my 3GS and downloading some games to it. Finding games, or even apps working with iPhoneOS 3 was certainly not easy. Right out of the box, EDGE connectivity worked flawlessly. I was able to SMS people, recieve and send e-mails, call people, and use most stock apps fine except Safari, Stocks and Weather.
Though a downside to this, is that apparently on iPhoneOS 3, you CAN NOT turn off cellular data. So I was stuck with eternal EDGE just, on.
Which wasn't an issue as I'm going to get into my next aspect, battery life.
The 3GS i did this on had a shit battery, would barely last 2 days in standby on iOS 6.1.6, however this thing completely caught me off guard. On an ordinary day this thing'd last me reliably throughout the day. From approximately 7:00 AM until 10:00 PM it'd only, ONLY, drain 25% of its battery. Keep in mind, this is all whilst EDGE is on permanently in the background.
Now on the other hand, the mac, OS X Snow Leopard really isn't that useful nowadays. Especially in the field of browsers. Suprisingly for Discord, there's an alternative solution. I didn't really use my mac for all that much, only for syncing my 3GS with iTunes and minimally browsing the web with old.reddit.com, and YT2009.