the number of hosts is kind of a fickle thing... when you log on you generally see more host than when you've been on the network a while. This is due to the newer clients that drop slow hosts and move them to the outside of the network. 3 ways to improve you horizon 1) increase your TTL 2) increase your # of connections 3) reset your connections every so often. (sometimes just due to people dropping off the network my host count drops to <100 hosts). Also it is dependant on what you are getting for hosts. if you are getting about 5,000 hosts then be happy that is actually a pretty good number and will satisfy most searches. If you don't find what you need amongst those hosts just disconnect and reconnect... this will place you somewhere else in the network and give you access to different people and therefore different files. Also some clients auto shorten you TTL's so don't get greedy with them. Meaning.... don't start increasing your TTL to 15 or something cause chances are they will be cut down to 7 by the first hop...this is something that must be done to reduce network bandwidth.

For info on this you should try:

http://www.limewire.com
http://www.gnutelliums.com
http://www.gnutella.wego.com
http://dss.clip2.com

all of these contain pieces of info on the network... but to date I don't think I've ever stumbled across an all inclusive FAQ...