I have kav on an isolated network, that does not need to be updated more then one a month. Is there a way to increase the time frame before kav will notify you that it is out of date?

In the admin kit, right-click on the group level folder these clients are in. Select properties. Select the Computer status tab. Double-click on the condition you would like to modify.

How about on the client itself? The client says the signatures are out of date.

I guess, you are completely wrong thinking that this is enough to update bases once a month for your network.
There can be two options here: if your networks is completely isolated - no network connections of any kind to internet, no floppies, the USB is disabled completely on the machines so that the users cannot bring their flash cards, no any other removable drives - in this (and only this) case you do not need any AV software at all... If, for example, the users are able to insert their USB memory cards into the machines in the network - you need to update AV-bases with almost same frequency as for any other computer. And our AV-software warns you about this. If you do not follow this warning - that's all up to you, you've been warned...