As they say, there are no guarantees in life save for death and taxes, however one can expect to receive a response to a query or request if the link to AES and from AES to CM that carries that request remains stable. Call control related requests use the CTI links between AES and CM and thus travel a different path than the first party requests and queries. Problems with the first party call control link would manifest as being unregistered. Problems with the CTI links would involve the application monitoring for link status events on the CTI link involved.

As to the interval that depends on many factors (mostly ongoing load and what the operation is). Registration requests take considerable interval to get a response (I have seen intervals in excess of 15 seconds), there is a lot going on to register a device. Whereas a lamp state query is often <100ms. Most operations are <1000ms.