Average share hold

I've seen it mentioned by a variety of posters that the average share hold is 48 hours, and how surprising this is. I'm going to try to show why I don't think it's that surprising.
There are at least two possible ways to assess average share hold time:
 Take a snapshot of all of the shares currently held and the length of time they've been held. Take the average.
 Take all of the share holds that there have ever been and the length of time they've been held. Take the average.
To show how these work differently, I'll give you a worked example:
Investor A  Ms Long Term Holder  £100 portfolio
10 shares at £10 each  held for 100 days before selling  currently held for 100 daysInvestor B  Mr Flipper  £100 portfolio
10 shares at £10 each  flipped every 2 days  currently held for 2 daysCalculation method 1, taking the average of all shares currently held, would take the above situation as follows:
Investor A's shares: 10 shares * 100 days = 1000 share days
Investor B's shares: 10 shares * 2 days = 20 share days
Average days shares held = total number of share days/total number of shares = 1020/20 = 51 days on averageCalculation method 2, taking all share holds across the period, assuming the index has existed for 100 days, would be as follows:
Investor A's shares: 10 share holds * 100 days = 1000 share days
Investor B's shares: 500 share holds * 2 days = 1000 share days
Average days shares held = total number of share days/total number of share holds = 2000/510 = 3.92 daysThe difference between 51 days and 3.92 days is clearly huge, and I think most people are assuming that it is the 51 days method that is being used. I suspect FI is actually using the 3.92 days method.
Also, flipping high value shares is a very difficult strategy to pull off, given how big spreads are at the higher end, so share holds that are flipped are likely of a lower value on average.. As such, we could easily imagine similar levels of total investment being directed towards long term investments and flips, and the average share hold being 2 days. As such, the 2 day average share hold makes sense to me.
Interested in your thoughts/whether I'm making any sense :)

@WillieMink Makes sense. Top post. What ever way they work it out the proof is in the pudding because after almost 3 years of trading only a small handful of shares have even made it close to the 3 year mark, if we believe Adam Cole and there is no reason not to.

yyyy, how Mr Flipper can hold 500 shares with £100 port in method 2??

@Mundek It's not 500 shares, it's 500 share holds over 100 days. 10 shares, sold and rebought every 2 days  i.e. 50 times sold and rebought in 100 days. 10 shares * 50 times sold and rebought = 500 share holds.
Hope that makes sense! :)

@WillieMink yes... hihi :]
But cant imagine there is many ppl like Mr Flipper even if they playing G&A strategy (new option) on cheaper players?!
Who buying and flipping after 2 days ??

I think it's more likely the pump and dump market is bringing the average down, those guys only tend to hold for 30 mins max by the looks of things  enough time to cause chaos, get money and get out.