Toning negs is not neccessary until you consider to inherit your negs to your grandchildren.
If you do so, Selenium toning is archival if carried to completion but will also increase contrast which is not desired most of the time. A viable alternative are Polysulfide Toners like Kodak Brown Toner (not formula T8, if you consider Richard Knoppows comments on this issue).
A good reference is Tim Rudmans Master Photographers Book of Toning.

Best

Stefan