Hi - Bamboo cores are used by a number of companies besides Liberty, including Salomon and ON3P, and I think DPS. According to people I respect, bamboo has some mechanical advantages, including being higher modulus, and consistent but light, as well as being moderately green. It's a very lively feeling core. OTOH, it's (gasp) mostly from China, so that'll be a no-no for some. Poplar is used everywhere, is moderately light and very cheap (like bamboo). Not so high modulus. The ash helps with that and stiffer, more consistent flex. I think that trying to find a "better" core is not the reason you should be picking one ski over another.
The lifespan will be more a function of how the core is put together with the rest of the ski, what other materials are used. For instance, "foam" cores are trash, right? Die in a season, right? Well, unless Dynastar or Stockli use them. In which case they're premium synthetic laminates. Get the point? Different feels and designs, so hard to compare directly, but Liberty makes nice skis, FWIW, and these days get as good/better reviews than Gotamas. I'd take a 2012 Helix over a 2012 Goat in a heartbeat. YMMV.