ellabee and Jane, thanks for the update on the stats and the numbers likely necessary to see an older title indexed. It's helpful for me to know in as much as which titles I may be more interested in indexing myself if not likely to be tackled "officially" (I just submitted what I think was my 6th indexing for review today, and was looking at what book I wanted to tackle next.)
I'm one of those with a high unindexed percentage in my library, because I tend to collect a lot of vintage/older titles, plus ones I pick up in travels outside of the US. It did frustrate me a lot at first, and even now less than 40% of my collection is indexed, but I still find the site extremely useful when I'm stuck for ideas on what to cook and don't want to just randomly pull titles off my shelves. I also like being able to quickly search through online recipes, too.
These days I also find it helps me decide which titles to buy when I'm shopping, even in used book stores. :) I can pull up EYB on my phone and check if a title is indexed or not, and that can be a selling point for sure.
And indexing a book is definitely something I enjoy, I only wish I had more time to do it as it really helps me learn the recipes in my books so much better. I definitely recommend giving it a try, and along with the suggestions made by ellabee about starting small I'd also suggest starting with titles in narrowly defined topic areas. That makes it a lot easier to learn "the rules" and how to do the basics without having to overly worry about every single topic at once. That is, I suggest starting with, say, a particular cuisine-foced book (Italian, French, etc), or type of dish (grilling, casseroles, desserts) that you like, then slowly building from there. I started with a seafood grilling book, then an Italian grilling book, then pasta sauces, etc. For instance, I'm not much of a baker or dessert person so learning the rules for sweet dishes has been tough for me...so I stick more to books focused on savory topics as it's not only more interesting and easy for me but more likely titles I'm going to use a lot in my kitchen.