Thanks for those replies and for explaining about that saddle. All nice bikes you guys are suggesting, though to keep it affordable i'd say the frame shouldn't cost more than $ 1000 or so. Cool.
Btw i wasn't suggesting we could pass on our bikes to our Grandchildren without replacing components now and then. I am just trying to find out which components are likely to last the longest and give the least trouble and still not be made out of 'unobtanium' or in 'la la land'.
How about second hand suggestions? Certain Trek frames that are sold often and cheap and are real durable, or..?