If you register a name in good faith, it does not belong to an internationally known company and you can show that you have a legitimate reason to use the name, you will probably be able to keep the name. This may not be the case if it can be shown that you purchased the name for the express purpose of re-selling it to a company with a legitimate claim to the name.
If there are no trademark disputes, your secured domain name will be yours for as long as you maintain the yearly registration fees.