Far too many to count. I find a diaper that works for what I need but I still try other brands out of sheer curiosity. Right now...the Abena L4 plastic backed diaper is more than I need for my purposes. However...I've found other diapers that greatly exceed my needs and I wear them too. Really...we are kinda spoiled by choice...and I'm totally OK with that. Its really nice having a variety of diapers I know I can rely on for at least 3 heavy wettings when I'm out running errands.
Also...if new diapers come out on the market...I want to try them too. I don't think that will ever go away.