I'm extremely lucky to live near so many LQS's. I actually buy most of my needles in boxes of 100. I usually use a coupon to get them. So since they don't cost much I change mine fairly often.
I have a marked pincushion for my needles. I used a Sharpie and marked the various sizes I use and divided the whole pincushion so I can find my still good needles and know what size they are. I put in a flower head pin in the section fo the pincushion to let me know what I have in my machine. Since, I too often change between different projects and they may each be using different needles.
It works. It is cost effective. It is fun.
ali
ali