@viraptor... You would need to retain the _time field after your first stats command runs. So you can use min(_time) or max(_time) function to retain the same and pass that on to timechart to plot count of bins over _time.
| stats count min(_time) as _time by clientip
| bin count as bins
| timechart count by bins
That's not really what I'm after. This will give me the time of the first request for a given clientip. It may approximate what I'm after, but the difference matters in my case. I want the results analysed for each (for example) 15 min span separately.