Questions about how jumbo loans work and how to refinance

[Freeman Schultz]

I have been researching jumbo loans and I understand how they generally work. But they raise some quesitons.

1. When does the lender contact the mortgagor regarding the principal? A year before the maturity date or the month when the principal is due?

2. How early does a mortgagor usually begin the refinancing process before the maturation date?