I'm curious about your choice to use T-Bills over simply earning interest on cash balance at IBRK. Looks like T-Bills earn about 0.5% more (~4.25% vs. 3.75%, so I guess if you're sitting on a lot of cash, that can be significant. But is that the only reason you go through the hassle and complexity of buying and rolling T-Bills? Is there a meaningful difference in risk? Always thanks for sharing and enlightening us.

There are two things to account for:
1. Even if you only keep $100,000 in cash, a 1/2% difference is $500 a year. That's a very nice bottle of scotch, or a rather fancy dinner out. Why give that away for no reason at all?
2. Even if you keep minimal cash, but have various cash balances as the year progresses due to buys/sells of other stuff, that cash should still be invested efficiently whenever possible.

As far as hassle/complexity, well I'm used to it by now. It takes me 30 to 60 seconds every Tuesday and every Thursday because I roll all the T-bills, and I roll them all manually because I often roll different amounts due to variable expenses each week/month. In the end, I have a somewhat higher average yield than if I just keep it in the money market fund. I'm probably getting 4.33% (T-bills) right now instead of 4.02% (money market).