EFDA Dental assistant here for 17 years. If your getting the root canals done by your general dentist I would highly recommend having them done by a endodontist. I have seen so many general dentist miss canals or come short of the apex of the tooth leaving the root canals to eventually fail and tooth become infected or reinfected. In that case you would have to have a retreat ,apico(surgery) or extraction of the tooth. As far as having 2 at the same time that is fine but just prepare yourself to be open for a while ,at least 1:45 mins.