I've got a rather nice US Type Set (1793-1964). It's my aim for it to be complete according to what's listed in the Red Book. I was creating a listing so I know where I might want to work on expanding my holdings in some issues. It basically works out to be a guide for me to know what less expensive coins there are that I don't have now and but might be interested in. Up until today I knew I was missing only two coins for my Type Set. Oops! Thanks to my new listing I discovered that I had some "holes" in what I considered a complete set. As of this moment I have added two more coins to that "missing" list. RECOMMENDATION: Do an inventory of your collection and review it periodically. That lets you know if there are gaps between what you think you have and what you think you are missing versus what your final goal is. Sort of like having one 1960 LMC for your collection and finding out there are Large Date and Small Date varieties.
Doing an inventory and periodically checking it over are good suggestions. At one point I had all my info scattered among invoices, written down notes, and memory. Setting up one excel document with all the information was very helpful and it is now much easier to track.
I have an Excel spreadsheet that I've maintained for the last 25 years. It tracks every coin I have ever owned, in great detail.
I have the opposite problem; in some cases, I've somehow acquired triplicates of certain coins and can't bear to part with them!
I understand your triplicate situation. I've run into that if I'm not careful with my inventory. I always feel I could have use the money spent on the extra to buy something else I didn't have. But once I've gotten them I don't want to let them go. BUT, I'm learning. I'm learning to sell off the extras.
