The phrase "accumulating over" is correct and usable in written English.
It can be used to describe the process of gathering or increasing in quantity or intensity over a period of time.
Example: "The stress from work has been accumulating over the past few months, affecting my health."
Alternatives: "building up over" or "growing over".
Running backs Braxton and Larry Watkins shared the fullback duties with each accumulating over 400 yards rushing.
He was a fans' favourite at Leicester City, accumulating over 100 appearances in his four years at the club.
We also completed our first-ever crowdfunding round, raising £2.6m and accumulating over 1,500 investors.
The warning signs about climate change and extreme weather events have been accumulating over time.
Much of the piece has an unsettled, brooding quality, with scattered piano pitches accumulating over sustaining pedal into dissonant clouds.
Another 3 trillion baht will come due as interest on the loans, accumulating over the next 50 years.
Measurements of the thickness of pollen layers, accumulating over decades on the bottom of lakes and bogs, suggest that growing seasons were becoming shorter.
"The driving force is the data that have been accumulating over the past eight years and that have been so compelling," Dr. Lenfant said.
Most of the plastic that has been accumulating over the past six decades has disintegrated and now consists of tiny fragments that cannot simply be scooped out.
Meanwhile, the number of papers describing cases of nutritional rickets in babies and young children in the United States has been accumulating over the past decade or so, from places as disparate as Alaska, Minnesota, Nevada and Texas.
Mr. Reiss spoke with scores of D.J.'s, musicians, promoters and fans, accumulating over 200 hours of interviews before editing the film down to a richly packed 88 minutes.
