You are right Duke, I will put the numbers of directory even higher and say there are thousands of them, most of them offer very little value and hardly any unique contents.
Most of them are set up mainly to boost search engine ranking.

Unfurtunately I am one of the guilty guys in this game because I have about 4 or more directories But two of my directroies are decent quality

There are indeed thousands of webdirectories out there. What I believe is the problem with all those (free) web directories is that none of them take even care to create a unique design but just use the standard template of the script.

I believe what adds value to the directories is the look and feel and the number of topics covered troughout the directory. I see many directories with only 2nd level topics, IMH not really valueable.

What I also think is very important that the listings in the directory have to be of a certain quality. That way it's attractive to visitors to return to the directory because they found a quality website at your directory.

It´s hard to drive traffic to the directories but than again that´s difficult with every other (new) website.

I believe it takes alot of time and hard work to create a big directory.
What I found to be some good examples are: http://www.uncoverthenet.com/, http://www.site-sift.com/, http://www.botw.org/, http://www.haabaa.com/ and others.

How many directories use bots to ensure their links aren't dead? Even human edited directories such as dmoz can't guarantee that all their listings work but bots would prolly be helpful to keep the directory up to date.

Is using bots to maintain a directory a good idea or am I just blowing wind out my rear?

I think ensuring link integrity either using both or a simple link checker is a valuable tool to ensure a directory contents integrity. I don't think most human edited directories have a link checker bot

So can you program this link checker to review all the links in your directory once a month?

yes,
I use submit wolf or something like that a few years back and it has that facility built into it. One of my web directory scripts (not mine) also has a built in link checker

See that's fantastic if it repeatedly checks links for you. I don't know why more directories don't use a bot or link checker software because there's plenty of directories out there with dead or expired links.