Do you keep GPS coordinates of the location of all these trees?
Unfortunately my GPS rarely works in the redwoods, I have coordinates for a few of them. I think exploring once a month allows me to keep most of them stored in my memory, or at least the general locations of them. If I ever wanted to go back and find certain ones, I'm pretty sure I could just print out a photo and locate it remembering where I was on each individual trip. Sometimes in my notebook I will record certain characteristics of an area to help me remember. All the trees in last year have been found in one general location, I'm just trying to systematically cover all the ground located there. Thankfully the terrain helps keep me focused.