I'm really not concerned about how long it takes a server to look through 700 files, servers are pretty fast.
My files are organized, all image files begin with pic, all boats for sale begin with s, etc.
It's like having 26 directories, each group of files starts with a different letter so they are all grouped together and a snap for me to find anything. I don't think it is a better way than using directories, it probably shows my age, lol. Maybe we had directories back in 69 when I started programming, I can't remember. But I do remember keeping things as short as possible so each instruction would fit on one punch card!

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Sailing Texas is a site I originally made to promote my sailing classes. It has taken a life of it's own, now the most popular part is the Sailboats for Sale section, and it just keeps expanding.
http://www.sailingtexas.com/