Anyone Using a Factory or Add-on Manual Choke?

as to the choke bi-metallic spring
On factory engines,the target for early LAs was 2 or 3 minutes; but I forget the ambient. Later models were faster.
Now; 30,40 or 50 years later, I treat every engine for what it wants.
It varies with a bunch of factors. On an already warm engine it might be on only several seconds. At 40 below with a direct-drive fan blasting it, it could be many minutes longer.