Absolutely.
My son has been long-tossing year-round since age 12 and has seen tremendous improvement. But it takes mental discipline.. 4-5x week with no excuses.
You can either 1) set up a net in your basement or similar area using a bucket of balls, or 2) Find a gym with a racquetball court and ask them if it's ok to throw against the wall (if concrete). This is what my son does.
Then, you may want to check out Jaeger's long-tossing program. When you throw for maximum distance, just raise the line-of-sight somewhat to simulate throwing for maximum distance.
Properly warm up! Good luck!