You are correct it is a huge task that has left me not really going through past images. I have images that I have not culled over the years and having so many it has become harder to make time to do it. Some I'm going to be surprised as I have not looked at them while most are not worth keeping. We both are photographers and between us have 28 TB worth of files. We have 3 32tb NAS boxes, one working and two off site.
I have gotten better the past two years since obtaining a nice laptop for traveling. Images at 14 frames per sec of wildlife can accumulate fast. I find culling through wildlife is must faster and easier than landscapes.
I have Photo Mechanic http://www.camerabits.com/ and that has allowed me to quickly view images, add a color tag, say red to delete, yellow for really cool and could look at at home for future use. After viewing a card I can delete all the reds and then if time allows go through them again. I can delete 60 to 90 percent per card before getting home. Photo Mechanic is so much faster than Lightroom.
Once home we upload though Lightroom and allow it to rename images. The yellow tags that were done in Photo Mechanic are read by Lightroom from the XMP sidecar file created by Photo Mechanic.
I do want to add that while traveling I have three copies of the images. Two hard drives and the original card. I cull images from one of the hard drives and when home that hard drive is uploaded to the server. My cards are never formatted until they are used again and formatted by the camera they are used by.
Rubberlegs if you shrink your images remember you can never make them bigger again in case you really want to do something with them later. Use the ones you are deleting as a learning experience, how can I make this better the next time. You could ask other photographers for advice from a photo club or.. Caution, family and friends will give you positive comments while great for your ego it's not helping you improve.