I get them maybe every 4-6 months. The doctor has to hit the right spot for them to be effective, so sometimes it takes 2 or 3 tries to get the needle in the right spot. It's done under a fluoroscope. My doctor charted each injection until I told him that I had relief. Now when I go for the injection, he puts the needle into the spot where he has it plotted on his paper and where I have told him I get the most relief. In fact, I am going today to get an injection. First, they give me a shot of Lidocaine, which does little to help with the pain of the injection into the facet. It's no picnic, but the pain only lasts for maybe 10 seconds and then it's over. For me, it takes about two days for the medicine (Cortisone) to give me relief. Sometimes, I get a nasty headache, which the doctor's assistant has called a Cortisone Rush. Lie flat when he gets home for the rest of the day and take some Tylenol or Advil, if he has a headache. It should be all better the next day.
I flew as a pilot for United for 34 years on long flights. Too much sitting caused my back problems. Bad posture, I guess. I had my L-5, S-1 disc operated on three times. I also have a bent coccyx, which I got from playing ice hockey and being run over by a huge dude. The problem with being a problem and having severe back pain is that I couldn't take any pain meds before flying. You wouldn't want to fly with me as your pilot if I was loaded up on Oxycontin. Whenever I took that stuff, I was already flying. Long haul truck drivers also are susceptible to back problems because of all of the sitting.
I wish your husband good luck and I hope that the doctor or surgeon hits the right spot for him on the first try. I should mention that the facet block is not as bad as an epidural, at least it isn't for me. My friend also gets these shots, but his surgeon puts him to sleep because he is a whimp. Like I said, the pain only lasts maybe 10 seconds and then it's all over and if your good, the doctor may even give you a lollipop. (lol)