8 almost identical bitcoin addresses worth $1.2b

[1Money]

I am new to this forum. This may have been discussed in the past, or it may belong into a different category. If so, my apologies.
   

I have looked at the wealthiest 100 bitcoin addresses (in terms of UTXO) and noticed a curious commonality between 8 of them. They are currently listed as #6 through #13.

What is it that they have in common:

1.    they all have a balance slightly above 66,000 BTC
2.   they have zero outgoing TX, never spent a Satoshi
3.    they all received their last input greater than 1 BTC in the time frame between 2014-11-12 and 2014-11-17. For each of them, this last large TX put their balances over 66,000 BTC
4.    they all have received fractional inputs since, but not many - maybe 15
5.    their very last input for each was on June 28th 2017, at 18:19:44, same block
6.    their first input TX was very close as well - for 6 of them it was on 2013-11-22, one of them on 2013-11-25, and the last one on 2014-02-24

Does anyone know or have an idea what's up with these? I was thinking, maybe a mixer? But that's a hell of a capital reserve, we are talking $1.2b. (I know the average buying price may have been 1/3rd but still). Also mixers need to send out some coin, unless ...

It's not the FBI's account (at least I didn't see any inputs from DPR 1FfmbHfnpaZjKFvyi1okTjJJusN455paPH), and not Mt Gox, I am pretty certain about that. Any takers?

Thanks in advance

[1Money]

So I found this TX which links the initial funding of all 6 addresses on 2013-11-22 to the same source
https://blockchain.info/en/tx/a289ea76bcc396412e90d63b90eb462ea2adb326aa027d5a1bb8864c7c152012

[anonymoustroll420]

2.   they have zero outgoing TX, never spent a Satoshi

This one is easy to explain. It is not good for security purposes to reuse addresses. Once you spend coins from an address, the public key will be revealed, so you should always move the rest of your coins to a new address.

Most of these addresses are probably long-term storage. The owners likely have other wallets that they use for day-to-day transactions.