Since they must be a very advanced race to do what has been reported over the years it might not take them that long to get here even if they live light years away.
Some people report multi-generational alien abductions. Thomas Reed would be an example of this. Bud Hopkins was told about early alien abduction cases that predate WW.I.I. So if you are an abductee who was abducted as a child then your parents could be abductees and any children you have could be abducted. If this is true it means ETs may have been coming here for some time. Human activity during the atomic era may have been a cause for concern if humans serve some purpose to these beings. Ufologist Robert Hastings for example has done a lot of reserch on UFOs and nuclear weapons. UFO incidents that occur around ICBM sites and nuclear power plants. Also humans venturing into outer space may be a cause for concern.
The truth is the Universe could be teaming with life very much like what you see in science fiction. Aliens may have always been aware of Earth and life on this planet but we are considered very primitive.