It all depends on what kind of keyboard you have, and if it has any sort of ghosting or NKR. Mine has full NKR so I can write
senipsenipsenipsenipsenipseni psenipsenipsenipsenipsenipsen ipsenipsenipsenipsenipsenipse nipsenipsenipsenipsenipsenips enipsenipsenipsenipsenipsenip senipsenipsenipsenipsenipseni psenipsenipsenipsenipsenipsen ipsenipsenipsenipsenipsenipse nipsenipsenipsenipsenipsenips enipsenipsenipsenipsenipsenip senipsenipsenipsenipsenipseni psenipsenipsenipsenipsenipsen ipsenipsenipsenipsenipsenipse nip
Without letting up, and I can do it with however many keys I can, but most keyboard are not set up with PS/2 or have any sort of psudoNKR.