Scientific documentation of children under the age of 7 has given serious weight to the legitimacy of past lives. I say 7 because the same studies that have documented the past life dreams have also reported them dwindling out at around the age of 7.

But I know you irl, and I've seen something you forget to include in this equation...something I've not seen termed, so I have basically given it my own name of "dream regression". Much like memory regression in hypnosis, dream regression does the same thing, except that the altered state is achieved through your sleeping pattern instead of a dangling pocket watch or a pen light.

I think a LOT of this dream in particular has to do with your latent ability to dream regress...and might actually relate to the fact that you bounce around different characters in your dream, picking and choosing what to alter and what not to. Almost like being lucid, but without having TOTAL control over the scape. As for the past life floors on this elevator... well that's got its own twist.

Fact :: The human brain treats memories as if they were actively occuring events (the reaction you had when you lost your dog years ago is the same physio-neuro-logical reaction you'd have today when remembering it). This being the case, our brains treat our dreams like every other memory. Ergo, dreams are treated like memories, which are treated like present events...so dreams are active events. Any time you have the same dreamscape occur, the same symbols will tend to rise up (the recurring animus, a fire that keeps growing from one dream to another, the same elevator each time, etc). Your past life memories are still in the elevator because they are treated like any other memory within the elevator scene.

Bottom line. Could be past lives. Probably also is just your brain regressing over past memories. Remains consistent because it's all treated as a giant memory.