If I have understood the paper "Secure Deletion of Data from Magnetic and Solid-State Memory" correctly, the use of 35 erase cycles is to cover every possible data format use by HD manufacturers.
However, if you know which format is in use on your particular HD, there seems to be no need to use all of them. Some manufacturers have this information on their web sites (Seagate do I think). So, a significant speed increase could be gained by only using the encodings which are in use.
However, if you know which format is in use on your particular HD, there seems to be no need to use all of them. Some manufacturers have this information on their web sites (Seagate do I think). So, a significant speed increase could be gained by only using the encodings which are in use.