Unfortunately I've just found out this week that Slack are discontinuing support for my version of Android. As my workplace uses Slack and I need to support the applications I work on, this means I'll need to either get a new phone or install a custom ROM so that I can get a more modern Android version. As it's my primary and only phone, the custom ROM route is a little worrying as it means I could potentially be without a phone if I don't have time to work through any issues that come up. Also, last time I ran a custom ROM, Google Wallet refused to work on my device.
So I'm effectively forced to buy a new device, despite being reasonably happy with the one I've got.