An automatic-renewal clause is not itself disqualifying. A continuing job and a temporary intended stay are different questions. Describe the renewal mechanism accurately and seek review of the applicant’s actual intent and requested period; do not invent a contract end date or assume that future renewals of status will be granted.
Separate the contract term from the intended stay
The contract governs the commercial relationship; the immigration question is what the professional intends and how long entry is sought. Those can legitimately differ. Describe the engagement precisely and let the requested period reflect the intended stay.
If the arrangement genuinely has no foreseeable end, that is a fact to discuss with counsel before filing rather than smooth over in the letter. One record usually settles the argument: the termination clause of the executed agreement. If either party can end the engagement on sixty or ninety days of notice, the relationship is not indefinite in any practical sense, and the letter can say so in the contract’s own words.
Where the clause carries no notice right and no outside date, the case is harder, and it belongs in front of counsel before the requested period is chosen rather than after a refusal. Note as well that TN classification is requested either at a port of entry or through an I-129 petition, and the same description of the arrangement has to hold up in whichever forum is used.