The best attribute type depends on the data, but it's not really important for actually importing. You can change it later if it helps for sorting or alignment purposes.
Duration is an odd duck. It is documented (
http://msdn2.microsoft.com/en-us/library/ms691006.aspx, PIDASI_TIMELENGTH) as being length in milliseconds, and with our test files, it does import but seems to actually be milliseconds*10,000.
Please send some files where these properties are not getting mapped. Thanks.