I do a serial back-up, always keeping at least 2 copies...
1) I put the images onto my Mac Book Pro HDD, and leave them on the memory card.
2) I put a copy on my network HDD (2TB time capsule;TC). I have 1 TB dedicated to photos. As soon as I do this, i format my CF/SD card and put it back in my card wallet.
3) I transfer the folder to an external 2TB drive (USB 3). I make sure this drive is up-to-date about once a month. At this point, I can free up some room on my MBP HDD (I usually have 150-200 gb dedicated to images on my laptop), having access to the files on the time capsule (TC).
4) When my TC is getting close to, or over the 1TB i want to use for photos on it, I move the older images over to my long term storage, a 2TB USB2 drive... it is slow, but works great for long term back up.
So, New images I have access to on my MBP for quick easy processing. Images taken in the last ~6 months I have network access to though my TC. All images are backed up on both 2TB external drives, one USB3 for working with and regular back-ups, and one USB2 for long term storage/back-up.
Old photos have 2x redundancy, some of the newer ones have 3x redundancy.
I use one lightroom catalog, and can easily re-locate the masters.... Also, the fact i have previews for most of my images on my MBP, it is easy for me to find and look at old images without having to plus in the external drive.
I will eventually need to get 2 more external drives, as my library gets larger... I think i am in the 1.7 TB range now. But I am gunning less these days and shooting more (less quantity, more quality, well that's the idea anyway). Then I will have two HDD for dates xx/xx/xx to yy/yy/yy (A and B i guess), and two new ones for the later images. It is not too much hassel. Just every now and again, i up-date the back-ups. As long as i have at least 2 copies i'm good!
I'm not sure if this is the best way, but it works for me, and I have my routine...