Its a best practice to initially search on smaller sets of accounts so when the save and refresh occurrs it only has to reload a few accounts vs all accounts.
One thing to point out, the more accounts you have in the screen, the longer it will take to run searches.
When you click save, the save not only saves the account details you just keyed in for the one account,
but it refreshes the dashboard.
If you had done a company wide search on a big company, and you had to wait 30 secs for all 15,000 accounts to load to screen,
and then you drill into just one account and make a change and save, it will first save that account and then it will re-run the search on the entire company to refresh all 15,000 accounts.