According to Schopenhauer, my dad should not have found the love of his life while in his 60s since reproduction was out of the question. I do believe long lasting romantic love is possible. I don't think you'll find it described in a romance novel. Perhaps so few philosophers write about love because it is so obvious. I imagine none of them wrote about the love they felt as children or the love they had for their children or grandchildren, but if they had children and grandchildren I am sure that at least some of them loved their children. IMO. the deepest love one will ever feel is the love one has for his or her children, but it is seldom wrote about in philosophy. However, I am not a big reader of philosophy, so it could very well be and I would not know it.
I dont know if age plays as much into it because mother nature is a wicked engineer. Look at the limits to which so many animals go in their mating process (bowerbirds for example). Would it be so far to say that we may be wired to pair up, regardless of the outcome? We are a social creature, and extended families have been shown to be an evolutionary advantage...
I think romantic love may be a difficult subject to analyze, as it is so very subjective. We have no real concept of the measure or intensity of someone else's love, and discover that even our own won't sit still and be recognizable long enough to study it ourselves, even. While the love of a child or long-term partner is fairly stable, I am sort of with old Schoppy on that romantic love is as much a fleeting incentive for our biology as orgasms are.
What do you mean is it an illusion? Do you mean does it exist? I'm thinking it does. I mean, of course it does. Even if it's a composite of several different things in a chemical soup we call a brain, as a concept and in practice yes it does exist.
I think the fact that we are still questioning whether it is or isn't lends to the argument that romantic love very well might be an illusion!
It might not be an illusion but it can surely disappear overnight whether we want it to or not and we have to push that reality out of our minds when we are in love if we want to be happy. We can do lots of things to "keep it vibrant and alive" but there is always a possibility that our love might not last despite all the effort we put into it.
I believe like everything else, love evolves. Ever growing. Ever changing and sometimes dying. No matter what kind of love it is. Right now, as my cat gets older and has health problems and needs loads of extra care everyday, my love for him is evolving with my growing acceptance that one day he will die. I think it's the same with people. Only with people things are a lot more complicated. Wouldn't it be nice if loving other people was as uncomplicated as loving your pet?
That depends on how you define "illusion". Do I believe romantic love exists because of the need for a biological mechanism to facilitate reproduction? Yes. Does that neccessarily mean it's pointless to adapt it differently? No. Regardless of it's evolutionary origin or "purpose", if you want to use that word (I don't like it), like all things with a phenomenological aspect to them, it can be adapted to your own wants, needs, purposes, whatever. Sure it's got a utilitarian reason for existing, but it still feels good, it still feels deep, and there is no reason why that particular aspect of it should qualify it as an illusion.
Now, I do believe that the popular image of romantic love is an illusion. Specifically, I mean this idea that there is a "right" person for everyone, that the relationship with that "right" person is infallible and infinitely strong and the strength of love will overcome yadda yadda yadd. Put differently, I categorically deny the idea that you can know that a relationship will last or be certain of anything about it. It can last for years, appear very strong and committed, and still die. I also deny that there is any logic to the partners most people pick, that it is really an arbitrary, chance-based choice, a child of circumstance mostly.