Accumulate over time is a phrase that refers to the gradual buildup of something over a period, often resulting in a significant or noticeable change. It can also be used to describe the continuous accumulation of knowledge, wealth, or experience. There are a few synonyms for the phrase, and they include 'collect over time,' 'incrementally build up,' 'amass gradually,' 'gather over a period,' 'stockpile over time,' and 'accrue over a duration.' All these phrases denote the gradual and progressive accretion of something over time. By using any of these synonyms, you can add variety to your writing and avoid repetitive language.