Another alternative. Is limiting the IP's that can access your WP-Admin using .htaccess Rules.
Which will save the overhead of running a plugin.

If you have a static IP all the better.
But mine at the moment is restricted to x.x.x.ALL as the IP Restriction, as the first three octets form the IP generated when I connect to my VPN provider.

So in order to access my blogs WP-Admin, I have to first connect to my VPN.
Does the job :-D

I echo Bob's sentiments of using a alternative username for the install created admin user.
I don't use admin of a combination of admin myself.