Yes the EM window of opportunity for US to be detected by aliens IS shrinking. The mainstream SETI thought these days is strictly focused on detecting beacons, if there are any given the possibility of "wolves". Folks like Harvard's Horowitz have correctly in my opinion moved their search to optical beacons where the SNR is orders of magnitude greater.

I'm interested in this topic although based on my reading of the literature I don't believe that there ARE any alien civilizations nor do I think it would be prudent to 'beacon' away if you were one. Only if you'd already colonized the galaxy and were in a position to detect emergent civs over time.