I have been accumulating when I get the chance (4c or less) - in June I have added around another 500K to my parcel. Three reasons: my other investments have been going well, the price is good, and the news we have been getting is positive. I would certainly hurt if MUS fails, but I won't be moving into the dog house.
I had seriously thought about going all in on MUS, but it is just too high risk for me at this stage of my life. If I was 10 years younger I think I would have. Plenty can go wrong that is totally unpredictable to risk a large chunk of my wealth.