I can't imagine going back to offsite physical drives anymore, such a PITA compared to the simplicity and ease of cloud solutions these days. Backblaze. Simple, cheap, fast (depending on your connection, but any pro should have a great connection if they are working). Do nothing, you are always covered.
I will consider using rsync that is build into the mac and a couple of scripts. Carbon Copy Cloner is a less geeky solution.
Here is a how to: http://help.bombich.com/kb/dmg-and-remote/using-carbon-copy-cloner-to-backup-to-another-macintosh-on-your-network
I am not a professional photographer (I work on systems), and I have a fast connection, but keep in mind that not everybody lives on the first world and fast upload speed could be difficult to find in many places. For someone working with a one megabit upload speed 32GB is more than 71h using all the bandwidth (no internet access then) under perfect conditions.
And I can tell you 1Mbit upload is the best home service in Costa Rica at this moment for ADSL.
As they say :
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.
—Tanenbaum, Andrew S. http://en.wikipedia.org/wiki/Sneakernet
In places were you have capacity caps (not in my country) it could be cheeper too, just copy the disk and ship it to a safe location and get the current location disk back.