I have been doing LED retrofits and two us could do about 12 in a day so your 1.5 hour idea is close.
what about all the other stuff? prepping, ordering and receiving materials, miscellaneous errands, permitting, inspections, etc? The way I see it, this job will demand a minimum of 80 billable hours. But I could be wrong.
When I did estimating the permitting would not be included in the labor unit time. Basically a permit will take the same time for one light as two hundred lights etc. permit costs vary widely in my area so that also needs to be handled separately.
As far as the receiving prepping and disposal.
The customer provided the fixtures and had them shipped to the shop, the receiver might have spent 10 minutes pulling a single pallet off a truck with a forklift and drop it in the warehouse.
On the day of the job I meet the apprentice 7AM at the shop, hooked up a small cargo trailer, loaded the fixtures, on the road before 7:30, on the job site by 8:30. One of us prepping while the other works on the new holes. All trash goes into the trailer, 1/2 hour lunch and on the road back to the shop by 3:30 PM. Next day apprentice empties trash from trailer into dumpster, disconnect trailer while I am in office doing other work.
So actually I already included most of the time for receiving prep etc.