Please see the section under “Treatment”/”When to have lower back surgery” for a full understanding of when to have and not to have surgery.
I assume you have no motor weakness as that is an indication for surgical intervention in my opinion.
The question is when to consider surgery if there is no motor weakness but pain and numbness are still present. In that situation, I think the window to consider surgery is three to six months after onset of symptoms. If your symptoms were somewhat tolerable but disconcerting and you underwent both therapy and epidural injections for the first three months without a significant drop in symptoms, you should consider a microdiscectomy.
Treatment alternatives include membrane stabilizers (Lyrica, Neurontin and the like), continued epidurals, continued therapy, home exercises and possibly acupuncture.
Dr. Corenman