I do believe in the tendency of time to take the path of least resistance -- like rivers, which I think make an excellent metaphor for time.
I would not have had any aspirin, because I'm allergic to it.
Same here on both accounts.
The mention of aspirin was a joke.
And a river is the way I picture a lifetime. When I dream of my roots, I see myself walking up a river. Otherwise, donwstream. A river does not reverse its course - except in its mouth when the tide goes up, indeed there is one thing stronger than a river - but in spirit one may go upstream... Aaaand this is going nowhere.
Now this is my favourite theory of timelines: in the multiverse, time branches out with each different decision, whether it's influenced by the future or not, (and with the different outcomes of random events?) thus forming different realities, the most numerous of which will have followed the path of least resistance. It's like the laws of probability.
So why bother to restore one timeline and make it like the other nine? Let's applaud the initiative which made that one different.
Anyway, until proven wrong, I think that in reality it may only be possible to travel to the future and not to the past... except if it's your return trip?? That might make sense logically but not scientifically.
Lastly, how can the job of temporal agents be to protect
their timeline? The very nature of their job places them out of any given timeline. How can they watch different timelines if they are stuck in one? And if they are free from any particular timeline, how do they choose between them?

Moreover, if they can watch different timelines at the same time, doesn't that mean that they all exist in parallel? What makes one timeline the master timeline?

Just food for thought. I think I need more justification on how a temporal agency can exist.