Do I Leave The Sweetest Girl In The World?

Side 1 says... I have been dating the most wonderful person I have ever met. She is sweet, kind, intelligent, caring, senstive, etc. She would jump in front of a bullet for me. We have been together for 3 years. The last few months, however, Ive questioned whether the relationship would be enough for me. We are both type B personalities and get along famously and never fight. Being Type B, I like little drama and people who are agressive, but i also find myslef a little bored and needing a little bit of spice or type A to balance the relationship out. (Again, we never fight). I dont want to hurt her and she is just as much in love with me as the first time we said it, but Im losing interest and running out of things to talk about with her. We have two different upbringings and many separate interests. The things we have in common is this mutual respect and love for one another. We are both good people. Do I stay in a relationship where I know I'll be loved and treated well or keep searching for that perfect person for me that ignites what I feel Im missing here. I feel Im getting older (35) and maybe this person doesnt exist? What if I get the excitement and great conversation from someone else but lose the loyalty and love im getting now?