the real point is day-to day, we never estimated; there was zero value in it. We did capture actual data though using our system, which made predictability possible just as I mentioned above.
This is a good post from Paul Boos giving an example of when estimates were not necessary. He also gives some examples of ways that he has provided high level estimates in quick manner.
Paul also hints at another trick for budgeting…
I limited the WIP of projects going on at any one time, so that I could keep my team close to constant size
If you have a constant team, the budget is pretty simple. What’s the cost of your team? That’s the budget for the year. So as long as you can keep the flow of work consistent you can keep the budget consistent. The real question then becomes is there any large or out of the ordinary for the year.
I highly encourage you to read Paul’s full post to see all his examples.