I did start a string diary and keep records of what I used. But really it does not achieve much because the string product range is always changing and sellers change catalogues. If I want some strings in a hurry, the local music shops only carry a very limited range of strings for all instruments not just ukeleles.
If you do find that you are starting to think about a string diary or such, sit down and ask yourself how your ukulele playing is progressing. Make sure you are not just thinking about strings or buying another uke to avoid the fact that you are not happy with some part of your playing activity and your brain is avoiding the issue. Your ukulele is a musical instrument, and you will get the most fun out of it by playing it, particularly in a group situation. Writing about your string choices wont make you a better player or get you out and about socialising with interesting people. However, if you are an avid collector and like keeping records and stuff, ignore the silly comments here and enjoy doing your own stuff.
