ebb and flow(1. to keep becoming smaller or weaker and then larger or stronger: Enthusiasm for reform ebbed and flowed. 2. to keep changing between two states: The battle ebbed and flowed around them. MED Alexander Demidov)
wax and wane(to increase and decrease over time:: Price-sensitivity is waxing and brand-loyalty waning. | Historical Romances continued to appear throughout the century, waxing and waning in numbers and popularity as public taste dictated.Andrey Truhachev)
