@kichae we do a lot of troupe play, with Ars Magica and Traveller, where each player has multiple characters. Either a Magus and their companions and grogs, or multiple crew members on a starship. It does take the load off the GM.
When I last ran Pathfinder, I had each player have 3 characters. They weren't normally played simultaneously, but it allowed players to take some interesting very specialist characters that wouldn't be useful in every scenario (I ran a more social, urban game).