(Spoilers for "what if")Yes the movie gave an explanation, but I feel it's insufficient. So the Ancient one tells us that the time stone will not let you see past the point at which it's weilder dies. However Strange is able to look into the future at the reality where Thanos is defeated. Therefore he can see past the point where he dies because he's resurrected. In the "what if" spinoff, we learn that the timestone renders it's bearer essentially ageless because Strange spent centuries devouring entities to become more powerful. So Strange is practically immoral until he is killed in battle. So why didn't he refuse the time stone to Thanos? They're always saying the time stone is "the chief weapon against the forces of darkness." Isn't it better to sling ring away from Thanos and save the time stone? That denies Thanos the full gauntlet so it might even save half the universe as well. But still does Strange never expect to need his "chief weapon" ever again for all eternity?