Measure a rate you actually have
Example: 120 completed rolls in 60 seconds is 2 rolls per second. Over two hours, 90% uptime gives 12,960 estimated rolls. The same rate takes about 92.6 minutes at 90% uptime to complete 10,000 rolls.
Keep the sample in the same mode and buff conditions as the planned session. If a potion expires, calculate the affected interval separately rather than assuming the first minute applies all night. The uptime field is your scenario assumption, not measured future availability.
See AFK setup, potions and luck for the limits of roll estimates.