The quest itself is quite simple to achieve. It's just pointless. There are very few teams that can run on full auto for brutal+, and for those that can, they often won't last to 150 turns. On manual it's quite easy to do, but you'll have reached your top chest reward long before reaching 150 turns.

Yah sure there are a couple of scenarios where those conditions won't hold true. Sure, there are some teams that can run full auto on brutal+, and sure, some of those teams actually will last 150 turns. And, sure, there are some scenarios where you're going to want to run on manual for as long as possible, because you need that damage to clear the difficulty for the clan as a whole.

But those are all super-niche, and, compared to the other Hydra quests, very silly. Like - how does decapitating 10 heads compare with running 150 turns? Like, I get it, it's supposed to be compared with the "Survive 50+ turns against CB". But the CB version is something any unkillable team can do.

Just change the quest to instead be "Deal X amount of damage on Brutal+".