Why do you waste time on this? Just find a HGE with >20 minutes lifetime - they occur literally in any system you jump in, and if none exist, just collect a pair of EGE there and HGE will appear.
Then fly to HGE, collect materials, and kill game process in task manager. Launch game, enter supercruise - and the same HGE will pop up back right next to you (less than 1ls almost always, often just several megameters). Drop back into it, and collect G5 materials again with limpets. Rinse, repeat. In 20 minutes you collect full stack of some G5 material. Go to material trader, and trade whole stack of G5 for lower materials in the same class - usually it allows to get full stacks for almost all lower materials (except a G4 probably, which will be not full). Go again to HGE, and replenish G5 to full stack again.
In this way, you get full stacks (300, 250, 200, 150, 100) for all five materials from the single "material class" (row) in about 1 hour.
Repeat 7 times for all material classes, and don't waste time on collecting pennies anywhere else.