"longtime commitment" is a correct and usable phrase in written English.
You can use it to describe a situation that has been in effect for a long period of time, such as a relationship, career, or hobby. For example, "She has made a longtime commitment to her art, dedicating many hours each week to practice and hone her craft."
And he reminded his listeners of his longtime commitment to their concerns.
She spoke of discovering the cancer during an annual screening, her excellent prognosis and her longtime commitment to breast cancer causes.
Through its longtime commitment to Wagner, the company has nurtured an audience eager to experience the "Ring" as all-encompassing theater.
But many investors may want to change funds simply to keep a longtime commitment to specific percentage breakdowns of stocks, bonds and cash in their portfolios.
His longtime commitment and leadership as a founder, former chairman and former president continued after his retirement and relocation to Florida.
Mr. Snow helped fuel that rally during a previous visit to Europe, when he appeared to abandon Washington's longtime commitment to a strong dollar.
Bryce, a running back, was a longtime verbal commitment to Miami who eventually signed with Tennessee before transferring to Kansas State.
Division I sports today require longtime full-time commitment.
The officers, Board of Directors, and staff of UJA-Federation of New York mourn the loss of Norman Cohen, longtime volunteer, whose dedication and commitment has strengthened our ability to help those in need.
Longtime disputes over commitments made under a partnership agreement have left both companies with bad blood.
Dr. Fred S. Berlin, founder of the Johns Hopkins Sexual Disorders Clinic in Baltimore and a longtime critic of civil commitment, said he was troubled by the scant use of antiandrogens.
