From another recent thread about PanF (emphasis mine):
Originally Posted by Chamaeleo
I've seen this as well with PanF, and have lost shots to films left undeveloped for a long time. I once ran a test and shot half a roll, stored it for four months then shot the remainder. The first half was noticeably thinner upon development. A month is not the end of the world, I myself wouldn't go longer than that without adding development time.
Originally Posted by bvy