We only have a limited time to exercise faith. Life is:
...a space granted unto man in which he might repent; therefore this life became a probationary state; a time to prepare to meet God; a time to prepare for that endless state which has been spoken of by us, which is after the resurrection of the dead. (Alma 12:24)
This whole world was created for the precise purpose of providing a space where mankind could exercise faith.
24 And there stood one among them that was like unto God, and he said unto those who were with him: We will go down, for there is space there, and we will take of these materials, and we will make an earth whereon these may dwell;
25 And we will prove them herewith, to see if they will do all things whatsoever the Lord their God shall command them; 26 And they who keep their first estate shall be added upon; and they who keep not their first estate shall not have glory in the same kingdom with those who keep their first estate; and they who keep their second estate shall have glory added upon their heads for ever and ever. (Abraham 3)
Faith in a particular belief can only exist until that belief has been physically proven through reaching the expected outcome. Experience is in some ways like sand through an hourglass—rendering beliefs into knowledge.
If you only act according to what is physically obvious, you’re wasting the opportunity of mortality. This is not manifested merely in the spiritual sense.
Consider the temporal outcome of those who refuse to do anything they aren’t forced to do. They live their lives in the squalor of the minimum required.
Consider those who refuse to think critically, sacrifice the present for sake of the future, and otherwise prepare now for what will happen later. They are reliably surprised by some disaster that was completely predictable.
If the principle of faith pays such dividends in temporal applications— and it does—consider how much it matters in spiritual applications, where one’s state will forever be determined through their willingness to exercise faith while in mortality.
What does it look like to make no sacrifices except those that seem absolutely necessary here and now? What does it look like to do only what is required spiritually? Ironically, Jesus never set a minimum standard because what that looks like is as infinite as the number of possibilities that are afforded through faith, but lost through inaction. He made plain that he requires not just everything we have, but everything we can be.
The time and place for faith is here in life. Even within this life, there are many situations that can only be affected through faith for a specific window of time. There are things you can do when you are young that you can no longer do when you are old, things you can do in plenty that you can’t do in privation, things you can do in health that you can’t do in sickness, and things you can do when you are single that you can’t do once you have a family.
Similarly, because knowledge deprives you of the opportunity to have faith, there will be times when your lack of faith in something has resulted in the loss of your opportunity to exercise faith in that thing:
17 Yea, there are many who do say: If thou wilt show unto us a sign from heaven, then we shall know of a surety; then we shall believe.
18 Now I ask, is this faith? Behold, I say unto you, Nay; for if a man knoweth a thing he hath no cause to believe, for he knoweth it. (Alma 32)
If you find yourself in a situation where you are compelled to believe in something—a situation where life presents to you such sufficient evidences of something that it becomes a sure thing to you, then the time to exercise faith has passed. You can no longer have faith in that thing, and the blessings available for doing so have passed you by.