According to the full technical paper of DROWN attack,
A typical scenario requires the attacker to observe 1,000 TLS handshakes, then initiate 40,000 SSLv2 connections and perform 2 50 offline work to decrypt a 2048-bit RSA TLS ciphertext
Among theses 1,000 TLS handshakes, one will contains the premaster secret decrypted, which will be used to retrieve the session key.
However, in my opinion, it will be useless if the TLS handshake is not the last one. In fact, after each TLS handshakes between the client and the server, the premaster secret will be different because the TLS session has refreshed...
Can you explain me why the TLS handshake containing the premaster secret decrypted, even if it's not the last exchanged between the victim and the server, will still serve ?