Delegation is not a donation. When someone delegates SP, he still remains an owner of that SP. And he can pull back his delegated SP any time, when he finds suitable. No questions asked. You as receiver of delegation can do nothing about this. Sure you talk to the owner, say him thank you, and maybe convice him to prolong his delegation for some time longer. No more.
Delegation is not permanent. Owner is a boss all the time. Otherwise who would delegate ?