It will take at least a year and 18 months might be the normal recovery period for Tommy John surgery.
From WebMD -
What Happens During Tommy John Surgery
During Tommy John surgery, a tendon is taken from someplace in the patient's body, such as his or her:
wrist
forearm
toe
hamstring (thigh muscles)
hip
knee
foot (Achilles tendon)
Sometimes, surgeons use a tendon donated from the body of someone who has died.
Surgeons drill tunnels in the ulna and humerus. The tendon (called a "graft") is passed through the tunnels. It is then woven into a figure-eight pattern to reconstruct the ligament.
To give the graft added strength, any remnants of the original ligament are attached to the tendon.
Mostly minor complications occur in about 20% of patients. The most common complications are ulnar nerve symptoms such as tingling and numbness. These symptoms usually go away shortly after surgery.
In rare cases, there are major complications such as:
nerve impairments
stretching of the graft
rupture of the graft
These complications can generally be corrected by additional surgery.
Tommy John Surgery Rehabilitation
Rehabilitation from Tommy John surgery usually takes about a year. In some cases, up to two years are needed for athletes to return to their previous level of ability. Other types of UCL surgery may not need this much rehabilitation.
Rehabilitation should be closely monitored by the patient's doctor and physical therapist. Some rehabilitation programs follow a three-phase process:
Phase I. After surgery, patients take these steps:
Wear a splint for seven to 10 days to immobilize the elbow.
Do gentle range-of-motion exercises for the wrist, hand, and shoulder.
Wear a range-of-motion brace to gradually regain full motion of the elbow joint.
Do exercises to strengthen the arm and shoulder.
Perform total-body conditioning exercises.
Phase II. Starting about six weeks after surgery:
Most patients can begin to perform elbow-strengthening exercises.
For at least the next four months, most patients are advised to avoid activities that overstress the graft.
Phase III. In the final phase of rehabilitation, patients take these steps:
About four or five months after surgery, athletes may toss a ball without a wind-up motion.
After six months, athletes may start to use an easy wind-up when throwing.
After seven months, baseball pitchers may return to the mound.
After nine months, pitchers may throw in competition if they are pain-free and have regained their normal strength and range of motion.
When surgeon Frank Jobe, MD, performed the first UCL reconstruction on Tommy John in 1974, he thought the pitcher only had a 1 in 100 chance of resuming his career with the Dodgers.
But John returned to the Major Leagues in 1976. He pitched for another 14 years and won 164 more games.
About 75% to 85% of today's patients can expect to return to, or even exceed, their previous level of competition.
http://www.webmd.com/fitness-exercis...ruction?page=2