A few lessons learned from years of legacy data migration projects

Sharing a few patterns I've noticed across projects, in case it's useful to anyone here:

1. The "silent errors" are worse than the obvious ones. Visibly broken data gets caught. A date parsed as text, or a duplicate row hiding behind a trailing space, slips through and causes problems downstream.
2. Validation rules matter more than the one-time cleanup. Cleaning data once is easy. Making sure the next export doesn't break the same way is the actual hard part.
3. Get a sample file before scoping the whole project. Legacy data is rarely as clean (or as messy) as people describe it upfront. A sample tells you more than a requirements doc.

Curious if others have found similar patterns, or if your experience has been different depending on industry/format.