Bumping. Interesting question I don't know the answer to.

Were they primered & good house trim paint on them? If so should last as long as trim on house also depends on amount of sun shining on them, more sun fast paint goes. At least that is my experience. On a covered patio could last for many years.

If you live in the tropics, where the sun and rain are hard on things, or if you live where it freezes, they aren't going to last outdoors as long as if you lived in a moderate climate.