without hitting AMT, I might think paying off mello roos might not be good based on some simple calculation. say 6K annual payment, pay-off amount is 10x, that is 60K, interest rate is 4%. 60K can become about 120K in 20 years. 6K annual payment with tax benefit will become about 4K annual payment. in 20 years, i will pay 80K total, still less than 120K.

but i agree long term uncertainty is another big factor…