had it lived that long
=if it had lived that long
虚拟条件句中的谓语中含有“had,should,were"等助动词时,可以把这三个词放在主语前,并把if去掉.这就是虚拟条件句的倒装.
不过,个人觉得,应该用：should it live that long更好,因为这是对将来相反的假设嘛.
如：
If he were here,he would help me.
=Were he here,.
If he should come tomorrow,he would give me much money.
=Should he come tomorrow,...
Had I known his address,I would not have phoned you.
=If I had known his address,...