I also found that the bubbles (or peaks, if you would prefer to call them that) seem to occur approximately every 234 days (an observation already mentioned on this forum) - with the minimum time between peaks being 213 days and the maximum time being 235 days. Considering there have been six peaks, that is a very small degree of variability for such a volatile phenomenon as Bitcoin.
It would be cool if someone could work out a root cause for this. It would be interesting if it was a slight mistuning in the Bitcoin protocol. Or perhaps a harmonic of reward halving.
Seems too regular to not have some factor affecting it, but once a pattern is established, it will be expected and therefore (potentially) self-fulfilling.