SA shouldn't run in background when notifications are not enabled and it isn't syncing.
I’d prefer to run SA the way I run Movescount. Open it when needed, sync, wait for it to be done, close it, done!
I don’t have notifications enabled, at least not without a fine filtering, so it seems wasteful to run the service in background so that it can sync the watch a few times per week. I try to maximize my phone battery life. Even if the app is mostly idle while in background, the process still takes some memory, and will make other apps more likely to be unloaded and reloaded, and therefore result in more battery usage.