To figure out how long it will take to charge the flashlight you use this equation

$$T=5R_{currentlimit}C$$

And for total discharge time

$$T=5R_{LED}C$$

Where

T is time in seconds

Rcurrentlimit is the power resistor used in charging the capacitors in ohms

RLED is the LED resistor in ohms

C is total capacitance in farads

One thing you should know if the capacitors voltage is lower than the supply voltage you should put capacitors in series to increase the voltage rating on the capacitors. Usually you should use 2 capacitors in series and the supply voltage should be no more than capacitors voltage times 2. The diode will drop the voltage by some and also prevent discharging it threw the wall wart

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