6 hours as the bottom limit for the time filter at the Graphs section is a lot.
The fact that you display the graphs with only 400px makes it hard to see the information in detail with 6hs of data being displayed.
Making the graphs wider will help a little bit, but I really don't need to see 6hs of information all the time. I mostly care about the last 15 minutes. I just want to see longer periods when something is wrong.