Concession or permission, depending on which version of the Bible you reference. Either is acceptable for the Greek, if you check your Strong's. The important point is that it is not by commandment.
Because Paul wrote it does it make it any less valid?
No, it's scripture, so it is valid. It's just not a commandment like you try to make it out to be.
I expect that Mary and Joseph, if they abstained, it would never of been longer than 40 days
Well, you are wrong already. Mary and Joseph abstained throughout Mary's pregnancy and Jesus was born of a virgin. Also, you've not proved through scripture that if they abstained longer than 40 days it was a sin. You can speculate all you want but you haven't proven anything.
The Bible says Joseph knew her in the sexual sense
No, it does not. You've been asked to show where this is stated in scripture, but you can't because it's not there. The scripture is silent on this point. All you are doing is making some assumptions.
Jesus had brothers and sisters
Where does scripture say these brothers and sisters of Jesus were born of Mary? Post scripture, not your speculation.
It already says brother and sisters. Post your NT writings where it says they're not really brother and sisters. No speculation please. The onus on you.
Me:The Bible says Joseph knew her in the sexual sense
You:No, it does not. You've been asked to show where this is stated in scripture, but you can't because it's not there.
I have posted it time and time again. But you would rather not believe it.
Matthew 1:24 Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife:
25 And knew her not till she had brought forth her firstborn son: and he called his name JESUS.
I was speaking of after the birth of Jesus.
On the Speculation Scale you both rate a "10".