How long do you guys tend to keep SQL migration scripts around?

Obviously they don't use up much disk space, but they do start to create clutter in a project

Based on your needs..

1. One time
2. Recurring

One time is easy kind of use and throw. Fairly customized.

Recurring is kind of complex must be dynamic if it is based on date or any criteria.

Mostly,
I prefer to migrator tools for one time.
Recurring in cron job.

We store them in folders by release number. So glad we do it, too. Was asked to restore a dev DB to an old backup (we keep those around too, for regulatory reasons) and had to apply eight releases of DDL so they could have old data in a current database with no additional DML applied to it. Mine is not to question why, mine is but to do or die.

Forever, because they are under version control.

Forever.