VTF and VTA- Constant or not?

I was wondering lately about the following questions:
What's your best, quickest method to prove that VTF and VTA/SRA have been set up correctly or close to ideal?
What tools do you need to have in measurements?

More important, I am pretty interested in knowing your invaluable experience:
Is it possible to have them "set and forget"(i.e. constant)?
If not, how frequent will you have your routine checking with the carts you have come across?

Any thoughts are welcome...
Thanks in advance.
Dan