a0d929ca_WSRP_v2_0_Specification__Statement_text
[#] CS202 [Section] 6.5 [Statement text] 
If the nillable response from getRegistrationLifetime is nil, then scheduled destruction is not in use for this registration and the Consumer MUST use the deregister operation to destroy the registration.
WSRP v2.0 Specification
Statement text