about:config
general.smoothScroll.mouseWheel.durationMaxMS = 1000
general.smoothScroll.mouseWheel.durationMinMS = 1000
general.smoothScroll.stopDecelerationWeighting = 0.2
mousewheel.min_line_scroll_amount = 5 or 60 prefer [50], If 60 is too fast (or slow) for you, you can change to a value that is suitable for you. Generally, the higher the value, the faster the page will scroll.
mousewheel.acceleration = prefer [ factor 1 & start 1] , Double click the “mousewheel.acceleration.start” entry and change the value to 1 or more (the value is the number of times the wheel is scrolled before the acceleration kicks in).
Double click the “mousewheel.acceleration.factor” entry and change the factor to the speed you desire. The default factor is 10, which means your scrolling speed will increase by 10 times when the acceleration starts. You can change it to higher or lower, depending on your needs.
Note: If this trick causes issue to your mouse wheel scrolling, you can disable it by setting the “mousewheel.acceleration.start” entry back to “-1”
general.smoothScroll.pages.durationMaxMS =1000
general.smoothScroll.pages.durationMinMS =1000
general.smoothScroll.pixels.durationMaxMS =1000
general.smoothScroll.pixels.durationMinMS =1000
general.smoothScroll.scrollbars.durationMaxMS =1000
general.smoothScroll.scrollbars.durationMinMS = 1000