Initially I did keep both, but after a month or two I found that I used the Sonnar lens for portraits and bokeh play. Subjects I would otherwise photograph with the Gauss lens would be close up shots using PK rings or product shots. The Gauss lens does have marginally better sharpness in my experience. The 135mm f3,5 Nikkor-Q.C however served this purpose even better, so after I observed the situation for 2 months and I noticed one lens always comes with me while the other one always remains in the closet I decided to sell the Gauss lens.
I still have the 105mm f2,5 Nikkor-P, an AF-S 105mm f2,8G VR micro Nikkor, an 80-200 f2,8 zoom, the 135mm f2,8 and 135mm f3,5 Nikkor-Q.C so all in all the range of short/medium telephoto lenses is pretty well covered by everything else in my camera bag. All the lenses I own see regular use. I don't keep anything on the shelf because I need to manage my rather tight funds for this hobby in a way that has me sell anything I do not use in favor of buying lenses that I actually use.
The only photographic item I have too many of is film bodies. I mean, who needs a Yashica TL Electro X, 2 Nikon F, a Nikon F2, an F3 and an FM? But that's mostly sentimental value there as most of those are family heirlooms and the FM my very first camera.