The answer to your question “Is it better to go ahead with surgery when the current situation is non emergent or wait till you can no longer tolerate the pain and the situation is emergent” is multifactorial. By understanding the risks of surgery with the risks of a non-surgical approach, you can make an informed decision.
Let us go over the indications for surgery in your case. Motor weakness, cauda equina syndrome and intolerable pain are the indications for surgery. You do not have either of the first two and you are improving with physical therapy so the third one is diminishing. Yes, there is a risk associated with living with the herniations but there is a risk with surgery too.
The risk of cauda equina syndrome is what appears to be your biggest fear if either herniation enlarges. Yes there is a risk but it is very small. I see only 1-2 patients a year with cauda equina syndrome from large herniations from a total population of about 1000 patients. Surgery therefore depends upon your risk aversion. The risk is 0.2% if you use the above statistics. The risk of recurrent herniation is about 10%.