No, trial accounts cannot be extended beyond the 90 days. Trial accounts can be converted to registered accounts by purchasing a device and using the new registration code included.

If you are using a trial account, you may create a new account near the end of the trial period. The new account name should be shared with your friends, so that they may add your new account to their friends list. The original account will lock after the 90 period and after 6 months the locked account will be deleted.