It is not possible to set dates for bug fixes until the cause of the bug has been found and a solution devised. With nastier bugs no timescale at all can be set at first, because nobody knows why it happens or even if a fix is possible.

When a fix is found, it must be confirmed by testing, review, etc. otherwise it is not known to be a fix.

When all that's done, only then, can a release timescale be set.

In general, there are two options, both with pros and cons:

1. Set goals, and be unable to say (reliably) how long it will take, only give estimates and ranges. This seems to be Nokia's way so far with the N900. (It is also my way when working )

2. Set times for releases, and be unable to say what will be included, only give estimates and have unreliable intentions. This is called timeboxing. It can encourage regular output, but the downside is people getting expectations about what will be included and being disappointed.