The adults may be dead but the eggs that hatch around August may not be so, be ready to apply the insecticide again. Since lace bugs are small and the nymphs are even smaller, the best way to identify them is if the leaf damage continues or reappears. They suck leaf juices from the underside of leaves so you need to look there when searching.

For tea scale in camellias, I apply oil emulsion sprays when the temperatures are below 85 degrees, as spraying at other times may burn the leaves. Reapply in 60 days if the problem persists but no more than three times a year. Scale also sucks leaf juices from the underside. There are several types of scale that attack camellias and they look different from each other. There is Camellia Scale, Peony Scale, Tea Scale and Wax Scale. You can locate pictures in the Internet by keying on phrases like "camellia scale pictures" or "camelia scale images". You can tell they are dead when you can no longer see them under the leaves and, of course, when the damage ceases and does not get worse.

The leaves will not recover much but, eventually, the existing leaves will be replaced by new leaves. In the case of deciduous azaleas, you will get new leaves in Spring. In the case of evergreen camellia sasanquas, they tend to drop the oldest leaves after a year or two, around May/June, so it may be a while before any damaged leaves are replaced.

The best way to eliminate lace bug is to move the plants to more shade. Some azaleas are more resistant to lace bug and do well in full sun, others require more shade. If you used a good contact insecticide on the undersides of the leaves you should have good control. A systemic insecticide should work also. I used to spray for lace bug when I was being inspected regularly by the Pennsylvania Agricultural Inspectors. Now that I don't sell any plant, I don't spray. I just try to place the plants in places where they are happy.

Here is a link that might be useful: Common Problems and Their Solutions.