We should not separate Jahnava from Nitai. I do not agree with this. Jahnavaʼs nam and mercy are included in Nitainam. She is supremely pleased when we take Nitainam, because it includes Her name. That is why Srila Narottam das explicitly instructs us to say Nitainam specifically. We should not create new sadhanas. Srila Bhaktivinoda always mentions Nitai Jahnava, not Jahnava alone. There is no Shakti without Shaktiman, and Shakti is included in Shaktiman. Just like we hide Radhaʼs name in Harinam by addressing Her as Hare, and just like we don’t feel qualified to directly talk about Her as She is supreme feminine form of Godhead and thus we freely talk about Krishna more, we should first feel safe to take full shelter of Nitainam and Harinam and talk about our Doyal Nitai sufficiently first before talking intimate things about our Jahnava mata.
Srila Narottam das Thakur would have said, “heno jahnava vine bhai” instead of “heno nitai vine bhai” if it was any more easier to get Radha Krishna by Jahnava’s name then by Nitai’s name. The fact is that Nitainam contains Jahnava’s name and is thus perfectly enough to grant us madhurya, along with Harinam. We are receiving Jahnava’s mercy through Nitainam, so why to introduce a new sadhana of Her name, which is not clearly mentioned in the scriptures like Nitainam and Harinam is? Nowhere in the scriptures it is said that Jahnava’s name can give madhurya faster than Nitai’s name?