HotM:Deterrence
Some buildings and flags require you to park Deterrence near them, and most of them increase how much you need based on the current turn number. So if it's turn 100, then it's a lower amount, and if it's turn 300, it's a bit higher. If it's turn 1500, it's going to be very very much higher.
So what's up with that?
The deterrence creeping up slowly is (almost, but not entirely) a psychological thing. It's meant to make you uncomfortable, but not meant to make you lose.
The best comparison point I have is the first boss fight in God of War 3, which was the subject of a GDC talk. Basically, that is a tutorial boss fight in that game, and it's meant to be easy. But it's also a very experienced god-hunter fighting and destroying an actual god. So... it has to be easy, but it also has to feel like you're getting your butt kicked. So they leaned into a lot of psychological signals that "wow you're about to lose" and "wow that hurt" and so forth, when really it's an incredibly tame fight.
It might sound strange to bring that ethos to a strategy game, but one of the essences of strategy is uncertainty, while at the same time players want to feel in control to a certain extent. So in other words, from a design perspective, deterrence could work a few ways.
First, it could just not count up, and it's perfect safety so long as your guarding units take no damage, etc. This isn't the end of the world, but it gives a sense of absolutism that I think isn't very thematically fitting.
Alternatively, it could harass you periodically, despite deterrence being there. In an RTS this is what I would probably do, but in a turn-based game, that is a lot of hassle to the player, for not much actual threat (or if it is actual threat, it slows down the game and creates busywork for the player).
Or, third, the option I went with, I can introduce a slight uncertainty with a very long time-horizon, but in a way that is known to stress players out disproportionately. This provides the feeling of danger, but you'd have to skip literally hundreds of turns without ever bothering to do anything like upgrade units or build more units for it to be a problem. It's super duper tame, but introduces a mild stressor that I think is warranted for this particular mechanic. The actual increase can't remotely keep up with your own power growth, so it's not a genuine threat long-term.
