I couldn't imagine having that much rare candies. I have just now managed to power up most of my favorite/most useful legendaries to level 35 or so (1 each of Moltres, Raikou, Groudon, Kyogre, Rayquaza, Mewtwo), and Articuno and Zapdos will be there after their respective months. Powering them up to max is overwhelming!
However, I think that even if I had the resources, I wouldn't want more than 2. I enjoy my variety (with everything except Machamp lol).