I ever read that it's advisable to register your domain name for at least two years. If you registered your domain name for one year only, search engines wouldn't take it seriously and your website associated to the domain name wouldn't easily get indexed. What do you think?

I have heard this before as well. To be honest though I don't think Google or other engines weigh the domain registration length very highly in their algorithms if at all. Just because someone Hasn't renewed a domain for several years does not mean the site is any more targeted for certain keywords.