I'm honestly not sure whether I agree with Shen Wei's decision or just understand it? Zhao Yunlan would have fought him on that decision so hard, and Shen Wei was barely managing to stay above water with the battles he was already fighting without having to contingency-plan for ZYL's contingency plans as well, so on that level I think it was the right decision. And, as someone else pointed out, even a kind one - they got to have their last times together without that doom hanging over both of them.

On the other hand, the fic writer in me wants to think that maybe ZYL and the SID would have been able to figure out some kind of workaround that would have saved the day for both of them. But given what we have in canon, I think I'm on Team Shen Wei's Sacrifice.