Added the following text on the interaction with rate limiting at the end of the
first main paragraph:

                                                        If the number
   of active routing state items corresponds to a rate of Queries that
   will stress the rate limits applied to D-mode traffic
   (Section 5.3.3), nodes MUST increase the timer for new items and on
   the refresh of existing ones.  A suitable value is twice the number
   of items divided by the rate limit in messages per second, which
   leaves a factor of two headroom for new routing state creation and
   Query retransmissions.

and the next paragraph resolves the Query timing contradiction:

   The Querying node MUST ensure that a Query is received before this
   timer expires, if it believes that the signalling session is still
   active; otherwise, the Responding node MAY delete the state.