It may be worthwhile to get some household flea spray from the vets. These spays usually last upto 6 months and take care of any eggs too! They can be quite expensive but if you only need 1-2 tins a year they're very economical. No matter how hard you try to keep them in, most cats tend to roam and I know its a long way off yet but if your house is already treated then you don't need to worry about it!
Congrats by the way, I love Kittys and have had a few and probably will again in the future
