They poop when they are ready to poop... they can get constipated, but unless there is something seriously amiss he will go when he/she is ready.
I had one male (RIP) that used to poop every six weeks like clockwork, others that decimate their enclosures every 4 days. Just depends on the snake.
My six week pooper, I got so excited over his lack of pooping skills I went so far as to give this poor lad an enema... yeah. Not fun for him, not fun for me.
Just let him be, he'll go when he's ready.
Bruce