This "you have to defend your IP" nonsense very quickly veers into propaganda in my estimation. Stated better here: https://www.eff.org/deeplinks/2013/11/trademark-law-does-not...
There is no realistic timeline in which the outcome you are suggesting comes to pass.
That's not at all how genericisation works it's really quite the opposite of abandonment.
The way one abandons a registered trademark, assuming we're talking about the registered rights [I only know about the un-registered rights in the UK, not sure what the scope of unregistered marks is in USA], is by not paying your renewal fees.
What it may do is reduce your damages claim to actual damages from the point when you notify the infringer.
Regardless, even if it were the case that one was required to notify all users there is always the option to offer a limited license for use of marks, so the layman idea of "you have to prosecute or you'll lose your mark" would still be wrong under such a regime.
Whilst the law is not logical, if you think about it allowing the law to work in the way claimed would actually provide a route to easily invalidate any [registered] trademark. One would simply use the mark for trade in a hidden way that the owner could not discover, the failure to notify of the infringement would then -- if the common wisdom held -- invalidate the mark and cause it to be abandoned. Millions of people would be falling over themselves to register Microsoft all the time because they were selling a product using that name and MS never notified them; it would be an entirely unworkable system.