Sri Ramanuja Munaye Namaha,

Sri Velukkudi Krishnan Swmai Guruve Namaha,

Swami says to follow Bhaktas own Panjangam for when to follow Rama Navami in Enapani 619 “When is Sri Rama Navami’

https://www.kinchit.org/kinchit-en-pani/601-650/

Also, below link shows the two types of Vratha that is followed during Rama Navami.

The Vratham on Rama Navami is observed in 2 ways.

* The first is to observe 9 days penance from Chithirai Sukla Paksha Prathamai tithi till Navami tithi. This penance is called Gramotsavam.

* The second type of penance starts from Shukla Paksha Navami tithi and continued for the next 9 days. This is known as Janmotsav.

http://www.livechennai.com/detailnews.asp?newsid=33612 

Adiyen Sri Velukkudi Krishna Dasan,

Uyya Oraey Vazhi UdayavAr ThiruvAdi,

Sarvam SriKrishnarpanam Asthu

Sri Ramanuja Munaye Namaha, 

Sri Velukkudi Krishnan Swami Guruvae Namaha, 

Mahalakshmi Bhagavata,

The prescribed penances for Rama Navami looks tedious to adiyen. 

Udalai varutthikondu oru sharanagathan vratham iruppadhu, Bhagavanukku ugappalla.

உடலை வருத்திக்கொண்டு ஒரு சரணாகதன் விரதம் இருப்பது பகவானுக்கு உகப்பல்ல 

If Bhakta’s intention is to do Vratham as a Kainkaryam to BhagavAn, then please do it to Bhakta’s Yatha Shakthi (to the ability what Bhaktha can do) as Swami says in Enpani 33 ‘Ability in Austerity’ for similar vratham on Ekadesi fasting.

https://www.kinchit.org/kinchit-en-pani/ 

Sri Velukkudi Krishnan Swami ThiruvAdigalaey Sharanam, 

Uyya Oraey Vazhi UdayavAr ThiruvAdi,

Sarvam SriKrisharpanam Asthu, 

Sarvam Sri Krishna Kudumbham.