Cement Board: Temperature Limit

[Papa Ron]

I am constructing a door for my oven, and thinking about using Durock as one layer in my door. It will be layered from the oven outward: 1/8" steel, Durock Board, 3/4" Insulation, 3/4" Cypress board. Everything will be bolted together, with 2 handles attached to the Cypress.

Is this over kill or what? What are the weak links?