Re: I am using Lr5 on a PC, working on RAW Nikon files. Without even touching the images, they lose their glossy vividness after a few seconds. What is the reason and how can I keep the originally vividness ?

Step 1: Adjust one image in Lightroom until you are satisfied with its appearance

Step 2: Use Develop->New Preset, select whatever selections you'd like in the New Preset dialog box (note: I always uncheck Exposure here, those probably need to be adjusted photo by photo)

Step 3: In the Import Dialog box, on the right, under Apply During Import, select the desired preset next to Develop Settings