H1B Extension - EVVC - with Client letter

My current I797 is expiring in Apr and this is my first extension ( No I140)

I work in EVVC model. I have the end client letter as well. Other letters are also available from both Vendors. However, the SOW end date is in Apr. Getting a SOW with extended end date isn’t feasible (End client’s policy of renewing contracts every ~4 months. Working with this end client over a year in the same format.). My attorney is concerned that I will receive RFE because of the sow end date.

How critical is SOW end date if I submit other letters?

It is very critical as USCIS gave new rules telling that everything has to be valid for the period requested on H1B. Read the news update on New H1B Memo