(Supposedly from Srikant Taligeri)
The common names consist of names having the following prefixes and suffixes: -aśva, -ratha, -sena, -bandhu, -uta, vasu-, ṛta-, priya-, and (as per the analysis of the Indologist P.E.Dumont), also bṛhad-, sapta-, abhi-, uru-, citra-, -kṣatra, yam/yami-:
In the Non-redacted Hymns in the five Old Books (2,3,4,6,7): NONE.
In the Redacted Hymns in the five Old Books (2,3,4,6,7): NONE.
In the five New Books (5,1,8,9,10): 108 hymns: V. 3-6, 24-26, 46, 47, 52-61, 81-82 (21 hymns). I. 12-23, 100 (13 hymns). VIII. 1-5, 23-26, 32-38, 46, 68-69, 87, 89-90, 98-99 (24 hymns). IX. 2, 27-29, 32, 41-43, 97 (9 hymns). X. 14-29, 37, 46-47, 54-60, 65-66, 75, 102-103, 118, 120, 122, 132, 134, 135, 144, 154, 174, 179 (41 hymns).
Except for the redacted hymns, not even a single hymn in the Old Books has a composer with a name with these prefixes or suffixes.
विश्वास-टिप्पनी
The above, if correct, seems to indicate that the mittanni branched off as the newer ones were being composed. Could be slightly earlier as well.
Suppose that the argument then is :
If 1600 BCE is the date of Mittani records, then the New Rigveda people must be at least 400-600 years before, for the travel to take place and establish themselves in the Mittani kingdom. That would be 2200 BCE where the New Rigveda was an established civilization
That would not hold water. Mogols did not take 400-600 yrs to overrun N India. Babur to Akbar was barely 50 years.