As we look to the spectra of stars from O to M type, we see that as temprature decreses, the spectral lines become more crowded. Why M-stars have more various elements than O-stars? Is that because of mass or age or what?
from http://www.solstation.com/x-objects/betelgeuse.htmLike many of the stars of Orion, it was probably formed a few million years ago from the molecular clouds observed in Orion but has evolved rapidly due to its unusually high mass. The star is a member of the "Orion OB1 Association," where massive young objects with over 10 times the Sol's mass can be found in abundance (more on OB associations and stellar nurseries).
http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_SystemIn roughly 5 billion years, the Sun will cool and expand outward to many times its current diameter (becoming a red giant), before casting off its outer layers as a planetary nebula, and leaving behind a stellar corpse known as a white dwarf.