use estimated build time instead of expiration time for delta when determining when to space out builds

llarp/service/endpoint.cpp

@@ -1205,10 +1205,10 @@ namespace llarp
       // time from now that the newest intro expires at
       if(intro.ExpiresSoon(now))
         return should;
-      const auto dlt = intro.expiresAt - now;
+      const auto dlt = now - (intro.expiresAt - path::default_lifetime);
       return should
           || (  // try spacing tunnel builds out evenly in time
-                 (dlt < (path::default_lifetime / 4))
+                 (dlt >= (path::default_lifetime / 4))
                  && (NumInStatus(path::ePathBuilding) < numPaths)
                  && !path::Builder::BuildCooldownHit(now));
     }