Well I had GTW for a long time and I hardly see any aliens in my game anymore. Once in a while I run into one that's in disguise but it's not a big deal. If you have a satellite dish on your lot or a telescope (I think?) it attracts more aliens in your town and more abductions. Other than that it's not a problem like it used to be. I haven't even seen any aliens spawn in my town in a long time to think of it. I used to just go into manage households and delete a bunch of them cause I hated having so many but I haven't had to do that in a long while.