Is retinal detachment surgery a permanent cure?

Possibly. Scleral buckle and vitrectomy are two surgeries that can result in long term stabilization of the retina. In many patients, this is a permanent cure. Retinal re-detachment can occur and requires repeat surgery 5-15% of the time.
Yes & no. It can be a permanent cure for the retinal detachment, however always at increased risk of it re-detaching. You should keep in mind symptoms to look for like those discussed by your retina specialist. Some are decreased vision, flashing lights, increased floaters etc. Consult with your retina specialist for further education.
No. Retinal detachment surgery even when successful can fail later on, this is why it is important to get routine follow up examinations by your retinal specialist.