Yes, it's a lot better to use series strings. The plus points are that there's no need for a voltage regulator at all, the overall system efficiency will be higher and the LED brightness will be well-matched, with very little variation from one LED to the next.
Each white LED will drop around 3.5 volts or so, which means that around 8 LEDs can be used (with a single series resistor) on 36 volts (allowing for the lowest likely battery voltage), or 12 for a 48V system. The individual series strings, with series resistors, can be connected together in parallel.
For 60 LEDs on 36V, then maybe ten strings of six LEDs, with just ten series resistors, might be best. The current drawn would be around 300mA, for 30mA per LED.
Jeremy
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