It always comes to this --- arguments about which metal is better for which thing.

To echo a previous poster, if you can't get reasonably priced steel, which you've already decided is your preference (hence no need for the arguments), then get aluminum in a reputable brand from a reputable dealer and be done with it.

If durability & longevity is what you want, then ignore the weight-weenie racing bikes and get a sturdier, somewhat heavier one. I'm sure it'll last you 20 years or more. For comfort, a carbon fork is a must. Peraonally, I'm not real confident about carbon seat stays because of that butted joint situation, but they might have sturdier joints out there as well.