Decreasing Term: This is where your life insurance coverage decreases over time, but premiums usually remain constant. This may be suitable for someone who has decreasing financially responsibilities over time such as a mortgage payment, auto loan, or student loan to pay off. If you purchase life insurance from a mortgage company, it is most likely a decreasing term insurance policy.
The cost is level, for the entire term of your life insurance policy with decreasing term. Just like the cost for "level term", is level, the entire term.
The term, is the duration of the mortgage. You can buy straight term life insurance for that long, also, if you want to.
And even though the payout amount goes down, the cost does not go down.
Many home owners choose to purchase level term life insurance for a term of 30 years, in line with their home mortgage loan, so they have guaranteed level rates and life insurance coverage for the entire period of their home mortgage.