I believe 3 buffers is the minimum you need for the CPU and GPU to be able to work independently and never wait for each other. Sure, one could queue up a bunch of extra frames and you'd have more margin in case of a multiple frames long stutter (at the cost of a lot of input latency), but you're typically better served avoiding multiple frames long stutters if possible. Triple buffering is, I believe, more about squeezing out all the performance you can from the hardware, not about just queuing up some number of frames which happens to be 3.