After resin infusion, and the part is cured at room temp. do you have to cure it in an autoclave to insure that the part doesn't deform, delaminate or get soft in the sun....?

No. The autoclave would be used during initial cure. It would by pressure, consolidate you stack more densely. Therefore less resin more fiber ratio and so a stronger part. What you can do is heat your cured laminate to 250f for an hour or so and the estimates I hear is a 20% strength increase can be had.

Fred