I don’t think I’d like to use the gift of foresight if it would cost me a day of life.
To me it sounds more like a curse: you could have the one-off events where you check to see the best time to get the bus and avoid the rain, but I also think you could go mad with the power. Not to speak of poor Cassandra, who predicted and predicted and was never believed.
Imagine being able to correctly predict next week’s Lotto, and hey, the draw is $17m. Great! (Though I’m fairly sure that’s illegal/unethical) And okay, so you don’t have to work which is great with your shorter lifespan. Only, it’d get boring not working. It’d get boring knowing what would come.
Or imagine knowing every time something bad would happen, and you couldn’t do a thing about it. Actually I’ve seen this trope in time-travel, when someone knows Horrible Event X will happen but they can’t stop it because of the chain of events unfolding and how things might get warped. It would be depressing knowing something will happen but for whatever reason you can’t stop it. Maybe because you wouldn’t be believed or because it’s Secret Knowledge, but either way not everything would be good.
And how would you keep track of the predictions/days used? Would you have to keep a journal of every time, or ignore it so as not to acknowledge how many days you’ve taken off your lifespan?
Life is short enough as it is. I see no need to shorten it by predicting things.