http://www.wholesomebabyfood.com/baby-food-freezing-chart.htm ............ says its safe to freeze, but the texture may change.
Stonyfield farms says...........
Does freezing yogurt destroy or alter the effectiveness of the live cultures?
You can freeze a cup of yogurt. A cup of yogurt that has been frozen and thawed will have a different look and texture than fresh yogurt. The cultures become dormant when frozen, but once thawed either in the refrigerator or by your body heat when ingested; they will become live and active once again. There will be a few cultures that do die, but there are so many billions in our products, that it is truly insignificant.
And that's all the say about that. Lol
I totally forgot... stonyfield makes those yogurt in a tube... we've frozen those (says right on the package to do it for a treat) - it was fine.
As far as how long, I'd assume you'd use the same guidelines for any other frozen food you'd feed baby.