I have begun doing this recently with the more common EDC knives I carry... I keep spares of my SAK Compact and Yeoman as they always ride in a watch pocket with a larger fixed or folding option for the day. Also, recently I picked up an additional Manix 2 plain edge in S30v to accompany my combo edge DLC S30v simply because I find them an excellent, sturdy and capable all around EDC option. I did this as it seems that Spyderco has a history of discontinuing models that I find useful.