This is my take on it. There's all kinds of love, and I think you can love people in different ways at the same time. So I think there's a "serious" or romantic love, a silly/playful/puppy love, a friendship love, etc. I like a mix of all in a relationship, and I don't think I'd be happy without a little bit of silly/playful/puppy love.
Like do you understand what I'm getting at? There's a time for the serious / romantic love; e.g., going out for a nice meal together, or spending the night together with some lit candles and a Marvin Gaye record.
Then you have your silly love; e.g., calling each other cute names, being playful, teasing, etc. Then there's time for the friendship love, which is probably kind of hard to give an example for, but you basically love them as a friend and try to care for them in the same ways you would a long-time friend. There's probably as many types of love as there are people, or at least letters in the alphabet, so .. don't get the idea this life is by any means exhaustive.
For me, personally, there is the "initial" stage which is probably characterized as a crush. If I get to know the person and I feel we're compatible in ways such as interests, values, life goals, etc. then my crush is likely to grow into "love" pretty rapidly. It's kind of hard to say where things go after that. I tend to find that the longer I'm with someone, the "more" I love them. . But it's not like you could really ever compare. What's the difference between year 2 and year 3 of being with someone? There's probably a difference between year 2 and year 5, but who is really keeping track? There's probably different types of love that you may feel apply to your partner as your stages in life change. So maybe you were ill or injured for awhile, and your partner took care of you. So while you certainly already loved them, you may find that you love them as a provider/caregiver more than you did before, or maybe more than you realized before they entered that role in your life. Or maybe when you're older you decided to have a family, in which case you may love your partner in their role as a mother or a father. I think if we all took more time out of our day to stop our minds and just admire the people we care about, we'd find new things to love about them.
Obviously there are physical sensations associated with love. Maybe they fade after awhile, but I've never found that to be the case with me. It's pretty hard to describe. Burning sensation in chest? XD A desire to hug the person until they pop? Ummm.. hehe.
Also, love vs. lust. That's tough. I think you can love someone and lust after them, but you can lust after someone without loving them. Are your desires purely physical? Let's say you were to go up to talk to them knowing full well that they wouldn't have sex with you within a year .. would you still want to talk to them? Would you be willing to be friends with them first? If you think "not worth it," then maybe you were placing too much focus on sex with them as opposed to having a relationship with them.
Fwiw, currently single but last relationship lasted 6.5 years.
(Man, that was hard to write out. I don't think I'll ever be confused for a poet.)