By your calculations it would take you about 3 months to make back the 1,200 you give up in smart rewards.
I'd say if that is the case it is worth doing as after that point you will be making more every month.
The only question I would have is: when you make a withdrawal from your Smartnode address does it affect the smartnode? If you need to restart the node then it might not be worth it having to wait the 20 or so days again.
Spot on. I’m still waiting for the next update to come out which hopefully reduce the initial wait time from 20 days to lesser day waiting. Also if I want to withdraw it would be on 25th right after I receive my smart reward. This is to maximise mu waiting time for the month.
Withdrawal does not affect the smartnode. The smartnode will still be in the queue.