Double-ended (DE) high pressure sodium (HPS) lights with electronic ballasts are reported to age more slowly than the old mogul base technology with magnetic ballasts, but aging has not been well studied in a greenhouse environment. Both dirt accumulation and age can decrease output.
Johnson, Jakob and Bugbee, Bruce, "Double-Ended High Pressure Sodium Fixtures Decline less than 6% over 2 years and 5000 hours" (2017). Publications. Paper 7.