Each installment has a separate timer, and it's an elective timer: it could start on either the date of each payment's receipt or the last day of the taxable year of receipt of that payment. The flexibility is pretty cool. If the installment payment flows to you via K-1, it's possible an even more flexible timing regime would apply as well under the K-1 rules. Therefore, no need to worry about deferring all at once: you may defer as installments are received.