Once you've checked off most of the worthwhile things to see in the world...
Although I'm sure this is at least partially relative to some of your interests I can't imagine anyone even doing this unless you travel for years and years and years. I have spend probably 5 years travelling in total and have a lot left to see! If you have 2 week vacations you'll never see everything in your lifetime. There are entire books dedicated to the 500 or 1000 things everyone should see and countless facebook posts with amazing places to see and people keep adding new things on a regular basis.
Have you been to Bhutan, the Taj Mahal, Tikal, Giza, Caño Cristales, Patagonia, Salar De Uyuni, seen the Northern Lights, Deadvlei, Cape Town, Plitvice Lakes, Dubrovnik, Mostar, The Hermitage, the Smithsonian, Mont Saint-Michel, Yellowstone, Yosemite, Grand Canyon, Victoria Falls, Ungoro Crater, Chobe, the Blue Hole, the Cenotes, Komodo, Jerusalem, Machu Pichu, Brugge, Istanbul, Persepolis, Bali, Kathmandu, Beijing, and of course Stockholm?
If you feel like you've run out of ideas for places to go then simply google one of your interests. Or maybe start a new hobby like diving or photography.