Could you direct me to a schematic to see please?
I do not have one, it was my guess at what would be needed if I had to solve the same problem.
The way I would approach it is:
1. join as many LEDs as possible in one chain, it simplifies the constant current circuit because the current will be the same through every LED if they are in series.
2. connect a transistor (MOSFET or BJT) at the bottom end of the LED chain. One transistor even if more than one chains are connected.
3. add a resistor (~1 Ohm) between the source/emitter and ground.
4. use an op-amp to control the conduction of the transistor based on the drop across the resistor, this gives you the current control.
5. for timing, use a simple MCU to produce the reference for the op-amp and switch it on/off as needed.
If more LEDs are needed than one chain allows, just parallel the chains with a small current balancing resistor in each.
This method uses far fewer components and dissipates much less heat.
Brian.