If you really want long term protection, get some Milky Spore and spread it on your lawn. This stuff is actually a bacteria that only attacks the larvae, grubs, of the Japanese Beetle. It won't hurt you, your children, your pets or any animals or birds. It starts working immediately, but can take up to two years to completely cover your entire yard. Being a bacteria, it relies on the grubs to spread the disease as they feed through the soil. I guess what I'm saying is that the bigger your problem the faster the disease spreads and the sooner you problem is completely resolved. The protection you have with Milky Spore is good for up to 20 years. So if the Japanese Beetles from your neighbor's yards lay more eggs in your yard, the spore are waiting to give the grubs the disease, no matter where the grubs are in your yard.