Estimates can be easy, or they can be incredibly difficult. I wouldn't advise pulling numbers out of the air, as they can make you seem incompetent when you end up waving at your self-imposed deadlines as they fly by. What you can check, though, are historical records:
- If your stored procedure is running and taking a while, start by looking back through your logs and trying to determine how long the last few runs took. The more data the better. If you've got logs going back two years, and you can see that the stored procedure took a few minutes to run at the beginning of its life, when the company was small and the database was smaller, then you might start to build a picture of a job taking longer to run, the larger the ...