If you read a spec sheet, most brands claim their bulbs have an average life of 2000 hours. Ever wonder why your bulbs never last that long?
The average life span assumes the projector is being used in a dust-free / climate controlled environment (yours isn’t) and is turned on once, never turned off, and running in a 24/7 application for 2000 hours (again, yours isn’t used this way).
Bottom line, you can usually count on getting about 1000 hours of life from your projector bulb.
Check your actual hours (your mathematic guestimate doesn’t usually work) in the menu of your unit. Don’t go into Easter week without a spare if you are at that 1000 hour mark.