It is astounding how many people fail to see the big picture/practical application of this topic in regards to us.
Will God punish you for accepting an antipope as pope and praying for him if he has not been officially condemned by the Church? Of course not.
Will God punish someone for calling a true pope an antipope and refusing to pray for him, even though God and Our Lady ask us to pray for the pope? Probably yes.
So just remember to make sure you have ALL of your "i"s dotted and your "t"s crossed before you become sedevacantist. And remember these quotes:
"Furthermore, we declare, we proclaim, we define that it is absolutely necessary for salvation that every human creature be subject to the Roman Pontiff."- Pope Boniface VIII, Unam Sanctam
"If by the Roman Church you mean its head or pontiff, it is beyond question that he can err even in matters touching the faith. He does this when he teaches heresy by his own judgement or decretal. In truth, many Roman Pontiffs were heretics. The last of them was John XXII."-Pope Adrian VI
"Pray for the pope, the bishops, and the priests"-Our Lady of Fatima/Akita