Can the symptoms of lumbar spinal stenosis wax and wane?

Absolutely. Yes, many patients with spinal stenosis will report that they have "good days and bad days".
Yes. These symptoms often times do wax and wane. Check out spine-health.Com.
Yes. They often facilate worse with activitu improve with rest they tend to cycle ad the nerve swells rubs more then with rest it shrinks and fits better as swellimg subsides.