I’m a little confused about what the situation is… When you talk about “letting” him be nice to you, what are you talking about? Just being friendly to you? You describe it as “friends with benefits, but not sexual ones.” So what do you mean? What are the “benefits;” what do you and he do together? Does he take you out for dinner, or to the movies, etc?
To be honest, as long as you’re being truthful with him, I think you’re doing everything you need to do. If you make it clear that you view him as only a friend and nothing more, and that if you go to the movies together, then it’s just two friends going to the movies and not a date, and you aren’t making out with him or whatever… Then if he still wants to pay for you and take you, because he likes your company just that much… well, that’s his choice.
Don’t do anything to falsely lead him on, but if he likes spending time with you, and you like spending time with him, then just the fact that he might wish it was something more shouldn’t stop you. He’s either willing to deal with that, or he’s choosing to hold out hope in spite of what you’ve said (which is his perogative), or he’ll eventually start seeing you as just a friend, or he’ll fall for someone else, or whatever. (Heck, who knows…? Maybe he’s right, and you’ll eventually see him as more than just a friend… ;-)
Just be honest and clear about how you feel about him, and if you both want to spend time together anyway, that’s fine.
Side Note: IMO, dating someone when you know it isn’t ever going to lead anywhere is only a waste of time if you’re dating them exclusively (in other words, if, by dating them, you’re closing yourself off from opportunities to meet someone where it would lead somewhere). But if you’re not exclusive, then dating can also be just for fun…