I'm quite curious as to if all hisses last a couple seconds and sound like hssssssss.
My bp has never done that, heck, he's never bitten me. He also never balls up anymore(he did frequently for the first few weeks I had him). Maybe he's just really docile? If it has something to do with the age or gender of a bp, mine is a little over 4 months and male.

As far as I can tell, he doesn't have any breathing problems so that's not what I'm worried about. But, if I hold him for prolonged periods of time(10 min+) at a time, he'll let out a quick sound similar to a hiss, but much quieter and shorter. Is this okay?