I agree. Apparently the inspired 18-month missions of a few years ago weren't cutting it. I know, I know...the official explanation is that the kids couldn't learn to be effective with a foreign language in that time. The 24 Month Boner (ouch!)
We have a winner! IMHO, the whole reason they do missions at this point is not to get converts but to solidify their existing base. Once they can do what they want with you for a couple of years, you are much more invested. I am happy to see more coming home early and in some cases, it doesn't appear to be a big deal. Dial it back 20 or so years and you would NOT see that.
They used to be 2 1/2 years for non-English speaking missions. My high school German teach was gone for 3 years. He's likely dead by now. I also once knew a guy who went on a mission in the early 1900s, and his mission was also 3 years. Former treasury secretary David Kennedy got married, and then was called on a 3-year mission to England. That's how it used to work.
The war started and he stayed in Tonga until it was over which meant he was there for at least six years. He said he loved it. When he got home he had to catch trout to eat raw because he couldn't digest a normal Utah farm family diet of spuds and beef.
I think long missions were common in Joe Smith's and Brigham Young's lifetimes. The men would go to England and return when their kids were grown.
Nowadays, I think asking 18 and 19 year olds to volunteer for two years is a lot. Non-Mormon kids who are church goers often travel with their church youth groups to third world countries for 2-3 weeks. They volunteer at immunization clinics or help build homes. They come back feeling that they've accomplished something worthwhile. They don't have to go for two years to feel that way.
I've often wondered if the Mormon church should reduce domestic or non-foreign language speaking missions to one year. That would give Mormon youth more options and might make domestic missions a more attractive option for them.