Deletions zero the corresponding entries in the addrs table, so if the deletion count was non-zero, then when you're through deleting all the expired entries, you run through the subnets table and load the remaining routes into the addr table.
Ok that sounds good, it should save a lot of time because most of the table is zero and never touched. I presume you do the reloading in order of decreasing subnet size so "nested" subnets are properly handled.
(of course nested subnets primarily occur in the case of BGP routed networks and in that case it does not matter too much because the traffic is not supposed to go via amprgw anyway)
Rob