What is the process and timeline for renewing a Non-O retirement visa in Thailand?

For information only - not looking for advice but hoping it helps anyone going through the process - if nothing else to allieve anxiety.

Hubby and I completed our annual extension of stay Non O retirement visa application yesterday at Hua Hin immigration. We had one small hiccup that was probably due to communication breakdown with getting the bank documents needed. We remembered from last year Bangkok Bank required us to request our statement and the letters of account verification from the bank so we requested those last week and the statement was ready. We had to re-request the letter which they produced yesterday - but they issued both on a joint document as we have a joint account. Immigration checkin (the lovely ladies that sit downstairs to go over your paperwork and let you know if you need anything additional to what you have before going upstairs and taking a number to be seen) sent us back to the bank to get second original (only needed if you and your partner are applying - she was correct that we needed it and it probably saved us from being denied) No problem getting it and we headed back to immigration. We arrived just before 12 so sat during their lunch hour and as soon as they re-opened at 1 were processed rather quickly with no dramas at all. Staff there are extremely helpful. It was an easy process and we both got our new stamp within around 15-20 minutes of the interview start. Cost us a whopping 1900 baht each and was pretty stress free.