I have thought about this quite a bit over the last day and the problem as I see it is that the Lubavicher rebbe puts together 2 and 2 and come up with results that he wants to. (My use of the present tense is not meant to signify that I believe he is alive 🙂 )
There is no Hakhel nowadays, and the year is not any more special that any other year, but we now have thousands of lubavichers BELIEVING that it is different (and perhaps more holy – I’m not sure about that), and that there is an inyan in making gatherings all year long.
Even when Hakhel did take place it was a once-off affair and did not last any longer than it took for the king to read sefer Devarim. (Perhaps there were other additional tefillos that I don’t know about. Please excuse my ignorance.) The year itself carried no more significance.
Ask a lubavicher and he will surely tell you that the year is special, even nowadays.
(I realise that I’m on my soapbox now, but why waste the opportunity…) It’s the same as lubavichers not sleeping in the sukkah. It doesn’t concern me that they don’t – why should it be my business? But what does concern me is that many lubavichers don’t even know that it says in Shulchan Aruch Harav that you have to, and that they consider those of us who do sleep there ignorant!
Another example is not eating Shalosh Seudos. I was told by a prominent lubavicher some years ago that to eat Shalosh Seudos is a “kulo al pi chassidus”.
In a nutshell, do whatever you want, but for Heaven’s sake stop claiming that your aberrations are the best way. They are not.