Yes, it's a necessity. But wrong timing (like, doing that before the previous gen achieved it's best exposure possible) and it may ended up with more mimimum-selling member instead. Though for NGT, I assume all has been done for the 1st gen at this point, unlike when debut single comes. The very same system also implicitly comes with more or less limited amount of member in respective group single senbatsu, the amount of opportunity that rarely rise in-parallel (whether it spread well or not) with the rising amount of member, and it doesn't even guarantee as much new fans as when the respective group debuted, resulting in higher gap of popularity in long run. And it's something that might affect the active member decision about the future. Sorry to say, but it is a utopia system that actually works if and only if the ratio of fans per active member were above the threshold. And when it doesn't, the equilibrium will comes by itself, either by the increase of fans, or the decrease of...... It's a blessing in disguise that NGT only lost 2 members in the span of 2 years. Something that some of us might have been overlooked in this stagnancy. Maybe by me too until recently.