I had recently problems with one of munin plugins - it disappear from munin graphs. In my munin-node.log I have a lot of:

[21134] Service 'temperature' timed out.

How to change munin timeout value? There is nothing about it in munin documentation. But if you look into source code you will find that it exists. Adding:

timeout 60

to munin-node.conf or your plugin specific configuration does the tick!