@lak,
“I use my Allnic L-3000 on the average of three hours per day (maybe more) seven days a week and have not had a need to replace any tubes yet.
I don't do any tube rolling because it came with very good tubes but I see no reason why you couldn't roll tubes.”
So how many hours do you estimate that you have in total on the stock tubes. Your average would be 21 hours per week, 21x4 (weeks) = 84 hours per month. What’s missing is the starting period to derive at the total hours used. Thanks.