[crestosssa]

Is it recessary to become entangled in speculation about literal post-mortem rebirth?

Not in the least. But the topic keeps rearing its ugly head.

Is it not enough to interpret rebirth as a series of different mental states we experience in the same lifetime?

What are your opinions on this? It is enough to disregard the term "rebirth" entirely. It is loaded with cultural and superstitious accretion and not necessary or relevant to the Buddha's teachings of liberation.