yellowing can be mitigated by using a heat stabilizer, not sure if the plastic you have available has it added form the supplier, but it can help! if bubbles are your main problem i would get a vac chamber to start, it helps immensely. as for time saving, using larger amounts in the microwave can help keep it hotter longer, but there will still be reheating required, but it can work until you get the presto pot.