Alto's Adventure

This will be one of the last achievements to unlock. You'll likely be traveling somewhere between 10,000-20,000 meters per run, and this achievement unlocks at 10,000,000 meters. Thus, you're looking at a solid 1,000 runs but likely more until you unlock this achievement. To put it in perspective, after finishing all of the missions I wasn't even close to being halfway done with the 10,000,000 meters. I was actually only a little over 1,000,000 meters, so only a tenth of the way done.

If you're farming llamas, distance will come naturally with saving llamas, especially if you play the game to collect llamas (method 1 in the "Llama Whisperer" achievement description). I was getting 100 llamas approximately every 10,000 meters so they were roughly on the same pace. If you're just going for distance though, naturally you should be playing as Tupa by this point so you can throw in backflips pretty much nonstop so you're always boosting when you're on the ground. With Tupa and a fully upgraded wingsuit you should easily be able to clear 20,000 meters in each run especially if you aren't concerned about llamas, but it's highly unlikely you'll be going for distance independently of llama saving.