When I was a kid (back in the ice age) I soon discovered that whilst the new CAM was eagerly awaited for all the new regies a good number of older "seen" regies would equally disappear. This led to my effectively making my own CAM which I typed out and diligently updated from various aviation publications. That way I never lost record of what I'd seen but was no longer in the published yearly CAMs. With the arrival of PCs I went the same way as HD and keep everything on Excel. You may find it a good idea to keep a record of where and when seen, c/n, as well as any pertinent notes such as if seen in a hybrid livery or with dual titles etc etc.