I've always had a tendency to hang on to my starter Pokémon as much as I can. It's probably because back when I was young and guillible, my friend told me that if you leave your starter Pokémon with Bill (these were the days of Red and Blue, of course), none of your Pokémon will obey you. But now I know that's not true so if I'm battling someone on Wi-Fi, I'll just throw whoever I don't need into the PC, but as soon as it's over, I'll normally take out my starter and leave every other Pokémon to rot.