More performance idea to a TIP

Author: DaveCTurner

docs/reference/searchable-snapshots/index.asciidoc

@@ -38,10 +38,9 @@ much data to searches for a given cluster size.
 
 === Using searchable snapshots
 
-A searchable snapshot can be searched just like any other index.
-{search-snaps-cap} are often used to access a large archive of historical data,
-for which searches may sometimes be complex and time-consuming.
-<<async-search>> is particularly useful for these long-running searches.
+A searchable snapshot can be searched just like any other index. Since there is
+a copy of the searchable snapshot on the nodes in the cluster its searches will
+perform similarly to searches on a regular index.
 
 The shards of searchable snapshots are also allocated just like shards of any
 other index. You can, for instance, use <<shard-allocation-filtering>> to
@@ -78,6 +77,16 @@ will be a brief window of time before {es} allocates these shards elsewhere.
 During this window of time the cluster health will be `red` and searches that
 hit these shards will fail or return partial results.
 
+[TIP]
+====
+{search-snaps-cap} are ideal for managing a large archive of historical data.
+Historical information is typically searched less frequently than recent data
+and therefore may not need replicas for their performance benefits.
+
+You can use <<async-search>> with {search-snaps-cap}, which is especially
+useful for more complex or time-consuming searches.
+====
+
 === How searchable snapshots work
 
 When you mount a searchable snapshot index, {es} allocates its shards onto the