There's only a limit on Pending (and WIP) Beatmaps, you can have as many Graveyarded beatmaps as you want.
As for using them all up, once you use up all your Pending Beatmap slots then you won't get anymore untill one of your maps goes to graveyard which usually takes around a month without an update. You can also get more slots by having supporter or getting ranked maps.
Hope that helps :3c