How do they work?
At Twitter, the refresher doesn’t vest until 4 years after grant date. This way essentially in your 5th year there is no cliff which a lot of companies have (I heard fb has a cliff). But at the same time you aren’t making bank the 3rd year and 4th year from stacked refreshers which I heard LinkedIn has.
Everyone's refreshers are different. I considered an offer from uber which was giving 50k stock refresh per year vested over 3 years. Airbnb gave 90-180k perf based vested over 4 years for my level. Refreshers are essentially a new stock grant which vests over 3-4 years (more commonly 4 years). Vesting of refreshers usually starts immediately upon grant and happens either quarterly or monthly.
In your 3rd or 4th year, the refreshers cause your tc to increase quite a bit. In my case in my 3rd year, I'll vest 25% of my initial grant which will be 105k. Plus, I'll vest around 25% of some amount of stock worth between 300-600k (based on perf for previous 3 years) because of refreshers.
After year 4, my initial grant becomes fully vested so my tc drops. At this point assuming you have not been promoted or gotten any raise, your tc would go back to what it was when you joined because you would only be vesting refreshers