Were Oil Barrels nerfed with advent of blessed lamps?

[Lokitia 56]

I have an off deed farm that I've lit with an oil barrel for quite a number of years. After the blessed lamps were introduced my lamps started going out. At first I thought I had let my barrel go empty but when I checked it still had plenty of olive oil in it. Every couple days I have to fill a few more and re-light them. Has something changed with the functionality of off deed lamps fueled by oil barrels? I can't exactly pave tiles in the middle of my farm so the blessing will work. (Well, I guess I could... but then I'd have 15 fewer tiles I can farm...)