Completely random usage

I’m a Plus user and have been trying to gauge usage and how much ChatGPT Work I can do on my plan.

I have one Work task scheduled daily, compiling information from certain emails into a summary list. Fairly simple, and I purposely do nothing else in Work to keep the amount of work at least fairly consistent (some days have more emails than others, but nothing significant).

I’ve been monitoring my weekly agentic usage each day after the task runs to see what percentage it uses (percentage of what is another question).

My account resets Saturday mornings. Last week, I was at 0% by Tuesday.

This week after Saturday reset and daily task run, I was at 82% full

Sunday morning after task run I was at 59% full

Monday morning after task I was at, inexplicably, 100% full

Tuesday after task I’m at 62%.

This feels as random as it can get. How can I plan any type of schedule to keep my usage from running out when there’s absolutely no limit transparency? I would consider the $100 plan that’s “5x” my current plan - but 5x of what?