Amen.
Time for a cool story.
Before 2008, I was working at a shop that used to publish one of the larger commodity indices.
It was a large trading shop too. So they just did not publish the indices, but would also allow you to take large positions for/against it.
The trader in charge of all these hated how slow the IT/Quants are. So he wrote some VBA code in a spreadsheet that would suck down prices from bloomberg, do some calc, and publish the indices back to bloomberg - all from within that spreadsheet!!
That spreadsheet was the index publisher!!
All these worked for 10 years. Then one fine morning, the spreadsheet decided to crash!!
For two hours, nobody noticed. Well, nobody but the arbitrageurs in the market!! They piled in! They would buy individual components, deliver them and demand creation units. Or they would buy the ETF, and demand delivery of unerlying components. Basically they were arbitraging the ETF price based on whether it was above or below the NAV!!
My employer bled some $50Million in 2 hours.
I was at lunch at around 12:30 that day. I got dragged from there to the trading floor by my manager, who seemed like his (non-existent) hair was on fire. The trading desk head demanded to know how many hours will it take for us to rewrite this thing so that it is properly reliable!!
Let's just say I spent a few days, and nights, working on that!!
Bottomline, if the ETF price diverges too far then most likely somebody is getting dragged from his lunch and being put to work days and nights to remedy that!! That should alleviate some of your worries.