Many thanks for the prompt response.
The original example was used to teach the concept of formulating process matrices (technology, environmental, scaling, production) to solve LCA problems (with Python). The functional unit was very similar to your suggestion, providing light in a house for 2 years. The assumption was made that 1 of the 5 lamps would break and require disposal during the 2-year period.
Within OpenLCA I generated a Product System of the most downstream process, disposal, as a way to capture all upstream processes. It wasn't that disposal was the functional unit, but rather I was trying to ensure all upstream processes were included. Perhaps I should be making use of waste flows.
I appreciate the quick feedback. I'll probably work to use a more realistic example in class.