Add another 7-14 days to each timespan to cover travel to/from the endpoints.
Arhus in Denmark, to Germany, to Switzerland, to the edge of Italy, to Greece via ferry, then to Cappadocia in Turkey : 2,983 miles. 100 days, 3.5 months. Padded to 4.5 months for exploration time.
Buenos Aires to Machu Picchu : 2,653 miles. 88 days. Four months, to include rest and repair time.
Rio De Janeiro to Machu Picchu : 3,438 miles. 114 days. 5 months, including rest and repair time.
Anchorage to Juneau, via Fairbanks, with a possible stop in Denali National Park. 1082 miles, 36 days. 2 months if we include ferry transport and exploration time. (A ferry stop in Seward to go kayaking would be an excellent addition to this.)
Yellowstone National Park, to Grand Teton National Park, to Denver, CO, to Arches National Park, UT, through Glen Canyon National Recreation Area via ferry, to Natural Bridges National Monument, to Monument Valley Tribal Park, to the Grand Canyon via eastern entrance. 1400 miles, 46 days. Six weeks. Padded to two months for exploration time.
Yellowstone to Bighorn National Forest to Buffalo Gap National Grassland, across the plains to Great Lakes via Minnesota, ferry across Lake Michigan, down through Ohio and Pennsylvania to my sister's place in Trappe, MD. 2153 miles, 43 days (50 miles a day average across the plains), padded to 2 months for time in the parks.
Lima to Machu Picchu.
One month, at an easy pace. There will be a lot of climbing and descents, but the scenery will be incredible. The coastal route through Pisco is easier, but has less fancy mountain sightseeing. The final stretch to Machu Picchu is via short railway, to a tourist compound with shuttles and many amenities. We could easily rest and stock up there.
We could also fly in to Lima, and then fly out of Cuzco (which is extremely close to Machu Picchu). SFO has direct flights to and from Lima, and direct flights from Cuzco. Flight costs would be around $1000 for each of us.
Dublin Bart through Yosemite to Mono Lake, down through Death Valley, the Mojave National Preserve, Joshua Tree National Park, San Bernadino National Forest, ending at my mother's house in Carlsbad. 900 miles, highest ascent 10,000 feet, lowest -240 feet. 45,000 feet of ascent total. 40 days, at 30 miles a day with every 4th day off.
From Portland up through Canada on the Alaskan Highway, northern route through Chicken and down to Valdez, across via ferry to Whittier, a detour to Seward, then up past Anchorage and Denali National Park to Fairbanks. From there, the option of proceeding north on highway 11 to Deadhorse, the roof of the freakin' world.
This is some extremely beautiful territory, but also quite dangerous in the last segment. 3750 miles total, with plenty of time for rest and exploration. Count on 20 miles a day or less, average. About 100,000 feet of ascent. That's a seven month journey.
This monstrous route starts in Shanghai and ends in Beijing. The interesting thing about it is, you can cut the distance almost in half, by getting on a train in Bayingolin on the far west end of the route, and riding it all the way into Beijing.
Considered as the full route, it is about 6000 miles. The partial route with the train is 3800 miles of biking, and about 200,000 feet of ascent. If you travel sensibly at about 20 miles a day you will be on the road for an entire year, factoring in the train ride and the surrounding travel and prep time.
You will pass right through central China, to Chengdu, then hang a right and ascend 15,000 feet into the mountains, down to Qinghai Lake, then west on the G315 highway through a sparse wilderness to Tieganlikexiang. If you're crazy, you can then head farther west and north, and ride along S165, the Shamo Highway, through the oldest, driest, and most remote desert in the entire world.