I have a 10 month old (mostly) American mini-pig/potbelly mix.
We've been taking the little guy on walks about 4 days a week. We'll go out around the block and interact with some neighbors and let him lead the way for some and explore. The walks end up being ~0.8 miles (~1.3 km) and we take around 15 minutes. The little guy even ends up running them some days when he's feeling up to it:
We realized we have a great park just a few streets over, so we've started trying that out. To get there, do a little loop and come home ends up being closer to ~1.4 miles (~2.3 km). And since he's still unfamiliar, he goes a little slower and roots every interesting smell in the grass. So we end up taking closer to 30-40 minutes.
While he seems to be doing fine with this length of walk, I just recently read some posts here about a healthy amount of exercise for puppies and how there is such a thing as overdoing it and injuring the animal (1, 2). I'd guess that the same is true for pigs. However, any searching I do results in tips for large farm or show pigs with a focus on not making them lose too much of their weight.
Our little guy is 10 months old and 15 lbs (6.8 kg). Is a 4 days a week ~1.4 miles (~2.3 km) 30-40 minute walk too long for him?