Let's say we have a backlog of User Stories, each with an estimated number of Story Points, and now we're doing the Sprint Planning.

Now, the Stories should be broken down into tasks and many Scrum resources suggest that each task should be estimated in person-hours. Since all questions have been discussed by the team at this point, estimating a task should not take longer than a minute. However, since a task should not be longer than a day, assuming a three week sprint with 8 developers means 120 tasks, and taking two hours only for estimations seems to be a bit much to me.

I know that experienced teams can skip or short-cut task estimations, but let's say we're not at that stage yet.

In your experience, how many tasks are there in a sprint* and how long should it take to estimate all of them? (Estimating only half of them doesn't make much sense, does it?)

(*) I know that depends on sprint length and team size, so let's assume 8 developers and three weeks.