Even the super HD #40 I use had to be adjusted after the first mile or so, but, onnce it took a set,it has not moved since.chains don't really stretch. i mean, the links don't get any longer.
when new, after a couple rides, it seats itself into the sprockets and all the links and rivets work themselves into place, that's what causes it to loosen up.
the rollers on the chain wear as it ages, that's why it's mistakenly called "stretch."
the teeth on the gears will also wear, and over time can develop a sawblade look to them from constantly moving in the same direction.
on older bikes, a lot of times a new chain won't fit on an old sprocket because the teeth have worn so much.
I literally can't remember the last time I had to adjust my chain. At least three or four months (almost daily use 25-75 mi per day)I did have to move the tensioner after the roller wheel wore into the new pattern since the #40 is so much wider. It made the alignment critical I always tack weld my tensioner which might help keep things strong and motionless even when coasting downhill or engine braking.
I have always told new builders the chain is the single weakest link in any stock kit. Even set up perfectly, the junk chain included with the kit is a failure waiting to happen.
I have a pile of stock kit chains.
I make bracelets out of them.