You are thinking that incidences of Force accrue? As in, having had less agency in one instance, you continue to have less in future instances even if no Force is applied? I'm not sure I agree with that, but I'm not sure I disagree with it, either, and I'm surely not inclined to argue about it.
Just to be clear, that isn't what I'm saying directly above. I'm saying "if Force deployment is a function of time, then more instances of Force will be occur in a game that is longer than another game."
Now, to address your point directly above, I would say the following:
1) A singular instance of Force will have a 1st order effect (
this thing happened right now rather than
that).
2) The significance of that 1st order effect will depend upon both (a) the stakes at the moment of deployment and (b) the downstream effects:
* Sam isn't dead, Cindy and Sam aren't dead, everyone isn't dead.
* We've gained/lost an asset(s)/alliance/enemy (The ranch-hand Timmy I had a d8 Relationship with in Dogs has been killed or turned against me, I lost 1 Coin/4 extra HP/spent 1 Adventuring Gear to make Camp and in DW to recover from the changed situation)
* The immediate situation subsequent to the one we're in becomes more/less dire or changes entirely (instead of being down a PC and having to deal with flagging resources because the fight went several rounds longer and we've still got a lot more dungeon to explore...we're much less tapped).
* Setting changes substantially (or less so) as a result (a Threat in AW is activated/created, our Lair in Blades is gone, etc)
* PC build or ethos or directives change as a result (a Belief in BW, a Bond in DW, Nature had to be tapped in Torchbearer, a Downtime Project has to be initiated in Blades, etc)
* Temporal or spatial changes occur as a result (a journey is now required, we've been ported to
n)
3) As one instance of Force turns into a 2nd instance of Force (and so on), the trajectory of play becomes more and more perturbed from what it would have authentically have been if no Force was deployed. Consequently, agency becomes more wrested from the players to the GM (and upon some fault line, a Railroad emerges which cannot be recovered from).