If the photon slows, then I'd expect that it's lifetime in its own frame of reference would remain unchanged. But I'd expect a reduction in its lifetime in terms of *our* frame of reference. Just an idle and non-profound piece of speculation. And it could well be incorrect, given the way that these physicists are forever making the workings of the universe increasingly complex ;-)

Okay. You asked for it. My profound exultations on the frame of reference of a photon.

Photons are the supermodels of the particle world; weigh (next to) nothing, rarely intereact with anyone but tend to cause heat when they do.

A dog forbid you should encounter a pair of them arm in arm; anything you tell one, the other will know instantly :)