This is happening because the 3D viewer caches for about 24 hours.
We know this is an issue (as it would be great that when you change the file the difference is seen right away!) so it will actually be fixed this week.
You should see all your updated models by Thursday, and from then on, when you re-upload a model, the 3D view will be updated as well without a long time lag!
Best,
Natalia
Last edited: Dec 17, 2012