It is a tricky thing deciding when and how much to open up the healing chambers. If the humidity is high and it is cool it can be done earlier without as much worry. I usually open my healing chamber for a minute after 48 hours to let in some fresh air and mist the lid and put it back on. I will repeat that the next morning and by the end of the fifth day I will leave the lid cracked. If no bad wilting occurs I will gradually open the lid more and by the 7th or 8th day will usually have the lid totally open. I try to give them a drink on the 7th day with very dilute fertilizer. I never put my plants in total darkness but just place a towel over the top and keep the healing container in a shady cool place for the first two or three days before allowing more light in.
My first batch done 7 days ago is now sitting outside on this cloudy overcast morning but I will move them into a more shady location as the sun gets brighter and hotter. In another few days depending upon how hot and sunny it is they will be moved outside permanently. That first batch has a few grafts that don't look great and I will know in another week how many survive but right now it looks like most of them will.
My second batch which was done 5 days ago has the lid off and I am checking it every thirty minutes for any signs of wilting and at the first sign of it I will mist the lid and cover them for a while before cracking the lid.
My third batch was done yesterday and I won't even look at them until tomorrow.
As it gets hotter I will have to be much more cautious about opening the healing chambers and try to keep them in a cool place as much as possible the first week. The exception to all that care about opening the healing chambers is when it is cloudy, cool and raining. When that is going on I just open them up and keep them on the porch until the rain stops. Depending on how long the weather is damp will determine whether I completely close the healing chamber or whether I crack the lid quite a bit. One time I was able to do two batches of grafts and right after I finished it started raining and it lasted for a whole week with no sunshine and the plants all healed without ever being closed up in the healing chamber. It doesn't get any better than that when grafting.
Bill