Benefits of series supercaps include: they allow for better energy utilization; simplify “dying gasp”/backup circuits, for example step-down vs. boost configuration for a 3.3V backup; and they are good for high power backup, industrial temperatures. However there are also the potential problems for series supercaps, including: they can have mismatched capacitances; leakage mismatches can cause overvoltage over time, the cells need continuous balancing; capacitance and ESR degrades over time and not always at the same rate; and supercap degradation is accelerated by overvoltage and high temperatures.