1. About 20-25% each person back then. Now, depends on how much we earned and how much to put back in, when we reach a certain ROI on investment.
2. SRR - this is cheaper alternative than buying a switched PDU.
3. I think its up to you and your goals. Any business has risks - the trick is managing, adapting and overcoming risks. So it depends what you want to achieve and what can you afford (dont sell the house) etc.
4. 50 years and above... age is just a number.... so much still to explore and learn. BTC & the blockchain, FINTECH, etc -- so exciting, so why not be part of that future. Mining ASICS... there is only Bitmain and Canaan - yes unfortunately.... quality control is still unregulated in the world of mining vs standard IT HW like server, network, CPUs, GPUs etc..... But to be fair, HW like S9 while not exactly perfect is a quite a machine. Same for A7s - its latest but has its quirks.... $/TH ratio is not as great as S9, while Bitmain's RMA process is not exactly a picnic - expect 1 month or more turnaround time. I guess that's part of the "agony and excitement" if you're a miner -- otherwise Bitcointalk.org will be collecting digital dust.
5. One of the investor is in the security business so yeah... we have to be vigilant at all times - plenty of bad guys out there. Our farm is not big just a small farm but we do run it like a business. GPU farm uses a combination of several tools like... Claymore's Ethman and AwesomeMiner.com. Of recent, I am also testing SimpleMining Linux deployment to further simplify things but I think we can't escape from Windows that soon because of GPU driver support, miner's preferences, learning curve etc.
6. Standardized on G2-EVGA 1000, 1300 and 1600 PSUs. Heat will always be the miner's nightmare - 4 slots or 6 slots format - the problem is the same because it runs 24x7. Always, undervolt to avoid overheating with plenty of fan RPMs -- better replace GPU fan vs replace a burnt GPU -- that's the cardinal rule IMHO. Also, Claymore's temp controls are excellent, so I use alot of his control switches. The 4 slot Biostars are target temp at 77c and hard stop mining at 95c. My wooden chop stick trick below is perfect solution for the moment and keeps them at check at 77-80c