There's a discussion on another topic that got around to year round throwing. Although the subject - year round throwing, wasn't part of the original title for the posting, it did generate some dicey exchanges with quotes being tossed back and forth from some pretty impressive sources.
This has been my experiences on the subject of year round pitching and throwing. For starters, I assume we're discussing the professional ranks and not amateurs. I say this because of the professional advice and comments quoted by various posters from the topic that I just visited. So, here's my take:
1. Professional pitchers that I've have experience with are as individual as they come. They'll do what the want, when and how no matter who tells them to do elsewise. Basically, these people are about as dumb as a fencepost and do they'll do the darnedest things in the offseason, like - snowmobile and get clotheslined by wire fencing, kicked in the cojones by a mule trying to impress a girlfriend, hang glide into barns, weeping willows and even hang upside down for hours all tangled up on a light pole. I even had one guy donate his time to a carnival by sitting on a stool over a dunking pool. Hit the target and the guy goes for a swim, The guy gets beaned in the left eye - out for the season. So, unless there is a specific place in his contract that says ... don't, they will.
The result of any of this finds our bright light tossing and pitching like every waking moment trying to get back in the swing of things. Which by the way is a stretch.
2. Some play ball year round in various leagues, here and south of the boarder. Money and contacts are the driving force here - not rest and recoup. I've warned some about doing this, only to fall on deaf ears. Bills must be paid, and that ole standby ... "maybe somebody, anybody, will see me and I'll get that shot to the next level." These guys are serious workaholics, and nothing will change that.
3. Another issue that often overlooked is a lack of self confidence. Constantly testing the waters for self impressions of accomplishments, again and again drive these guys. These kind of drives are not only dangerous, but in the short run, they're career enders.
Now all this being said, for the amateur regardless of the level of competition year round pitching, not just tossing the ball around, can be problematic. With the youth leagues, overuse and playing with two or more clubs simultaneously can have, and will, ultimately lead to health issues down the road. A youngster is still growing, developing muscles and supporting tissue has to have time off from the demands of pitching. Coaching that's short on proper health and maintenance, player immaturity, and that ever drive to win, win, win, is a mix that just begs for injury.
I recommend taking a break in the offseason, relax, goof-off, give the body a chance to come off that tuning-fork mentality. Heck, in just a few short months, we'll be back at it again.
Besides, for the amateur, the offseason usually grabs hold with social responsibilities, school, family commitments, personal relationships (now there's a learning curve that bites), part time jobs, and so forth.