Great topic, and dear to my heart. I started keeping a journal about 15 years ago, and when I began it I digressed to my childhood days when I began hunting with my Grandad, and recorded all the significant hunts I could remember. Like you I sometimes make short notes, other times lengthy ones. I note the dogs, guns, shells, locations, successes and failures, and even glue in a lot of my expired hunting licenses and duck stamps on the facing pages.
I must admit, I don't do this for myself. I realized, when my two grandsons began to show an interest in hunting with me, how important a journal of my "exploits" could be to them someday after I "cross the river". I have thought so many times what I would give if my Grandad had done so, and left it for me to be able to read and relive his hunts vicariously. I have his guns, an old duck call, and some pictures of him in field and stream, but no handwritten notes. I hope it will be as special to my grandsons as that imaginary one would have been to me. From what I am seeing of them as they mature into men, I think it just may.