I have kept track of my sightings for years. I have also moved around a lot.
My master life list was recorded in my copy of Clements' Birds of the World--a couple of years ago that book came up missing. I am hoping the next time I move, the book will miraculously reappear, since all of my European sightings are there. My nightmare is that it was in the trunk of the car I sold a few years back, and I didn't notice when I cleaned it out. I can't imagine why that thought has been bouncing around in my head for years, but it is a recurring nightmare. It has GOT to be in this house somewhere.
I keep my field notes in little notebooks I can carry around, and some of those are missing.
I tried AviSys, but when my computer hard drive died, so did my list.
I have been meaning to start using eBird for some time. My hope being that once the sightings are posted there, they cannot be lost. In addition, the information entered by birders is a source of information for many scientific studies.
eBird is another project of one of my favorite organizations, Cornell Lab of Ornithology and the Audubon Society. I am going to spend some time over the next several weeks going back through all of the notebooks I have and loading that information while inputting information from my current birding outings. Let's hope this eliminates my observation storage problem while contributing to the general knowledge about birds.