When conducting cross-chain operations, it is necessary to ensure that the final_tlc_expiry_delta of the inbound invoice is greater than the overall expiration time of the outbound invoice. Otherwise, the inbound invoice will be reclaimed upon expiration while the outbound invoice is unlocked by the preimage, which will result in fund loss for the CCH node. Currently, the constraint is set as inbound.final_tlc_expiry_delta / 2 > outbound.final_tlc_expiry_delta. However, this constraint overlooks a scenario: if there are too many routing nodes for the outbound, the tlc_expiry_delta of the entire router may end up being greater than the inbound.final_tlc_expiry_delta.