How long might it usually take for cranberry juice to ease the symptoms of uti?

UTI: Cranberry juice or pills does not cure bacterial cystitis or relieve symptoms to any significant degree. The only possible benefit is in taking it daily is to prevent bacteria from adhering to the bladder epithelium. If you have cystitis, see a physician and have a urine culture and get appropriate antibiotic treatment. Meanwhile you might try one of the many "azo" products otc for symptoms.

Agree with Dr Krick: Cranberry juice sometimes helps as a preventative but not as a treatment for UTI's. Cranberry juice can help to prevent urinary tract infections (UTI's) in women with recurrent UTI's because of the proanthyocyanidins (PACs) it contains.