Prevent
I am an engineer and I have to say, that making turrets degen when out of range for more than 60 seconds (make the range decently far away, but not half a map) is a really good idea. In some instances it might even help me as an engineer.
I had a particular problem once where I was fighting mobs on a ledge (champ) and I got kicked off the ledge. I didn’t die, but my turrets were up there. As long as my turret was fighting I was in combat mode. That meant no waypoints or anything. But at the same time, I was scared to destroy it, for fear of causing the other 2 people up there, to possibly die. So I had to run (it was all the way around the mountains, through a cave, and up) back to the ledge. And I had to do it in slow mode, since I was in combat.
In some cases, like deployable turrets and the supply pack, you don’t necessarily have the option to destroy turrets, and the despawn would help with that too.
Anyway, I got off topic. Even though I’m an engineer, I agree with the whole despawn when out of range for so long idea.
I have even done the turret bit, though I stay in the area. I’ll usually plant a turret on one side of an event, then go to the other and kill there. I get credit for a lot more kills that way, therefore receiving more loot.
I’d see this as an exploit and report it accordingly, since that is, essentially, what it is.