saving jpegs in another format?

[Sally Mack <photographs.by.sally.mack2@xxxxxxxxxxxxx>]

When I get my film processed, I order CDs as well as prints.  The files 
on the CD are jpegs which I then edit.  I understand from various 
sources that the jpeg format loses data.

Should I save the jpegs as tiffs or some other file format?  If so, at 
what point should I save in another format, immediately, before editing? 
 After editing?

I use both Photoshop and Vuescan (thanks for the suggestion, Karl).

==Sally