Every couple of months or so, few tweaks.

Just... whenever I realise I like a certain princess more or less than another.

It has changed a lot since I came back from hiatus, but it has been mostly solid now.

Kind of what JungleQueen said, whenever I realize something about a princess that I hadn't noticed before that makes me like or dislike them more. My list has stayed the same for a few months now but I might make a few tweaks.

About every.. 5 minutes I think?

^ Haha xD
My list changes pretty frequently. I'm constantly fixing it every few weeks or months.

Don't really know how xD

I don't even have a list, I just have a favorite... and maybe a second favorite.

Only when a new movie comes out, and then the change is fitting in the new DP more than anything else.

Let's put it this way: Pocahontas was my favorite until Mulan came out, Mulan remained my favorite until Tiana came out, and Tiana has remained first since then. I've changed my list only twice since joining fanpop a year ago, and that was to move Merida from second last to fifth, and switch Mulan back from #3 to #2.

Eh. My list always had Ariel near the top. When Mulan came out, Ariel became second. I don't mind the other DPs who are in the middle. But both Tiana and Elsa slid right down the list to the bottom because their movies irked me, and the girls themselves were mean people who reminded me of cliques.

Ever since Frozen came out, Elsa has always been first on my list. She's complex, smart, has a real interesting story arc, is caring towards her sister and her kingdom (Elsa isn't mean in the slightest. She's always seen being nice towards the people of her kingdom even when they don't return the favor and has an undying love for her sister. Elsa refuses even touching her own parents just so they don't get hurt, and is very warm towards Olaf when she first meets him. Elsa, for the snow queen, is an extremely warm person) Elsa also goes through a real and admirable development, has grace and class, isn't afraid of giving up the good and going for the great after her kingdom shunned her out, and admits her mistakes when she must. Elsa also isn't ever petty nor does she keep grudges, just keeps the memory of her dead parents and acknowledged their rules for her. I always felt meh on Tiana untilI re-watched TPATF when I grew up, and then I absolutely adored her. Tiana went from about 8th onto my second place spot on my list. I loved Tiana's sass, her determination, how kind she was towards her parents, how she developed over the movie from being a stick-in-the-mud into a fun-and-hard working-girl, how she isn't afraid of telling people off who deserved being told off, how even when Charlotte was selfish Tiana still loved her, how even when Tiana became the princess she never looked down on people and always kept the people she loved in mind. Tiana also shows selflessness in giving up the dream she worked EXTREMELY hard for so that Naveen and her could be together. Elsa and Tiana have been my top two for a year now and I don't see it ever changing. Same...for Ariel. When I was younger, I always loved Ariel. I loved how she was a mermaid, I loved how she was cute, and I loved how she was a redhead like me. About a year ago I re-watched TLM and realized how WRONG I was about Ariel. I saw that she was bossy, self-intitled, mean towards everyone, was like any other ditzy and uncaring girl from high school, doesn't give a crap about authority, whines about her life all day long when Triton was trying his best keeping her satisfied yet nothing was ever good enough for Ariel so she whined some more, learned absolutely nothing from the movie, doesn't care about anyone else's dreams or feelings, is a complete drama queen, and cared more about a guy she never met then her own friends. I don't think these three spots on my lists will ever change. While everything else has gone back and forth in the past year, Elsa and Tiana being my top two has stayed the same, and Ariel has been my least favorite has stayed the same also.

Mulan is still number one...

Besides Ariel's matter, usually only when a new DP comes, I rearrange my list.

I may or may not move Belle to my second favorite but Mulan will always always be my number one

It depends on the section of my list. My top 4 don't change much, but I occasionally switch others.