Alternate ports is not really any protection.
I'm not sure I agree. 99.97% (an arbitrarily made up but probably not too far off
number :-) of the stuff you see on the Internet is bots and scripts, and these don't
adapt to non-standard ports. Breaking in would require a human to sit down and some time
figuring out what I've done. Admittedly it's not that hard, but the odds of a
real person wanting to spend his time doing that is pretty small.
Having said that, I also don't enable keyboard authentication on my ssh servers -
it's public key/private key only.
Bob