My daughter Vicky and I (Ginny) play a lot of your games, especially the 10 Days series. Like many, we have combined the games for longer trips and really had a lot of fun playing all 4 - 40 Days in the United States of Eurasiaca. Later, I saw that you posted your own rules for 20/30/40 Days on your site.
Now that the Americas is out, we have expanded our game to 50 Days in the United Americas of Eurasiaca! I have included a couple of pics below.
Set up is you pick 10 cards from each game, then toss the rest in a big bowl. You mix the 50 cards that you picked, then randomly place your cards starting with the top row, left to right, then the next row, left to right, until all rows are filled. Use 4 or 5 discard piles instead of 3.
Same play as the regular games but the draw pile is just too big! So instead you pick from the bowl! You can use cars, boats and planes interchangably, i.e., you can use any yellow plane to go between any two yellow countries all over the world. You can also use cars for games that dont usually have cars.
You must have at least 7 cards from each game set to win.