That's why I kept it vague lol

If I limit the definition of "love", or even what it is based on, then any responses may be influenced by me, rather than the responder. It would be like asking, "What's your favorite food ? Pizza or Sushi ?" A person may come back with some other food entirely, but at the same time, I may have indirectly influenced them to be thinking along the lines of Italian, or Japanese ... etc. So I tried to be vague. If I added to it, it was to get the ball rolling.
For example: suppose a person believes that their love will benefit the other person, and this brings them great joy. So even if they had foreknowledge that at some later point in time, such a person would leave them (let's keep it simple and just say "leave", not necessarily betray with thought out maliciousness) ... perhaps they believed in love itself to the degree that they valued love so much, they believed it was a treasure worth sharing, even if it was just for a time. Or let's say that their very nature was loving, to the degree they would willing sacrifice aspects of their own life for another ... even if it meant the other person may not even care about it one whit, or may even throw it on the ground. What if some point later in life, after such a person left ... what if they had a change of heart years later ? Learned that they actually valued what they had before ? And that it actually DID make a difference in their life at some point ?
I even kept the scenario "vague" for that reason as well ... because suppose there is a scenario where there is a CHANCE that the person would later return and have a change of heart ? Or what if they didn't ever return, but took the love that was given to them finally and passed it on to others ?
By keeping it vague, it lets the responder respond with the scenarios that they/themselves can imagine. For example, I would immediately think of such a scenario: where a person may leave, but what if there was a chance that the love and devotion shared would EVENTUALLY pay off in such a way, that it benefitted them in the long run ? What if they had kids, and even passed it along to their own children ? What I did today, would reflect in the future, even though I may not see the physical result the way I would want to right here and now. And this relates right back to the OP in a lot of ways ... consider Hebrews 11 and the list of individuals who supposedly didn't receive certain promises in this life, etc, because their reward was elsewhere. But I didn't want to directly bring any examples I may could think of up, I wanted to see what any responder may or may not consider.