I did the JMT in the summer between my jr and senior years on college, so it was not a huge interruption in my career or schooling. That and my other trips in the Sierra were life changing for me. They made me think that backpacking and outdoors activities were a way of life, not a recreational activity.
After college I put all my worldly possessions in my Ford Falcon and drove to Washington state. Before leaving CA, I rode my bike around Lake Tahoe, and hiked in the Immigrant Wilderness. Day 3 in WA I climbed Mt. Rainier. I had $400 and 5 lbs of soy beans, and spent the summer doing week long hikes in Washington and Canada. After Rainier, the Enchantments, Holden Village to Darrington, Revelstoke, Cascade Pass and Sahale Pk. I went back to Wenatchee and found a job when I ran out of money.
I worked September thru June, then quit the job and did another 3 months hiking in Washington: the Olympics, Alpine Lakes, the Pickett Range, the Ptarmigan Travers in the North Cascades, and lots of time in the Enchantments and Stuart Range.
The next summer I also took off 3 months for hiking; ElDorado, the Ptarmigan again, Enchantments, Mt. Stuart, Rainier again, Rampart Ridge, Tuck and Robin Lake, and the upper Enchantments via Colchuck Lake many times (no permit required in those days). I saw more of Washington in those 3 summers than people who live there all their lives. It was probably a setback to any kind of career, but what I ended up doing is totally different than what I planned to do anyway.
I don't take the big chunks of time off now, with mortgage, business ownership, and kids in school, but I get out as much as possible, including at least one 9 day backpack. Now its with my son, so that is a huge bonus. Have a great trip!