Thanks for the input.
I'll also be using a Lutron RA2 VCRX garage door receiver, which connect to the GDO contacts and allows control of the GDO from my HomeLink car visor buttons, as well as lighting scenes.
I emailed RA2 tech support, and they said to avoid connecting the VCRX to a GDO with a 'smart' panel. Seems that the GDO contacts supply power to the Smart Panel, and could damage the VCRX if wired in parallel.
The Chamberlain Smart Panel can only be used with specific GDOs. It's not just a simple contact closure input on those GDOs.
I guess I could wire the VCRX to a remote, but I think that's a project for the next GDO that fails. The others look to be less than 10 years old, the current one is 18 years old, manufactured in '94.