The golden rule of editing images on a pc is, NEVER work on the original file.
Once a file as been saved then reopened, the save command should be greyed out, so you should not be able to select the save command. If you make a modification then "Save As" the quality will be impaired, to a certain extent this impairment can be minimised by using the maximum quality setting in Photoshop this will be setting 12.
If you go the Tiff route this will as you say Preserve the images at their present quality. You will however see a major increase in in file sizes, so consider available storage capacity. Two Jpegs one as master and one as a copy, (Two jpegs will take up far less space than one Tiff) to work on will probably be the better way to go, unless your camera will shoot Tiffs or you decide to go the Raw route
My method is to shoot in "Raw" then convert to Tiff. Both files are then saved to my dedicated photo h/drives. The only time I would convert to Jpg is for posting on the web