Not sure if I need Slush's permission to call the API but I have limited the refresh to 10 seconds minimum for now.
As a pool operator, I would recommend making the auto refresh interval measured in minutes, with 1 being the minimum. Most people will run this in the background and rarely look at it, so having constantly up to date information is just adding load to the web server+database without much benefit. It's one of the reason most pools removed/never added live refreshes on their websites: Most people will just leave a tab open and forget about it.
Would be nice if slush added a anti-refresh measures. And maybe some other api for "vip" clients, if they so want. If you want to constantly spam refresh - consider a little donation.
Or even funnier method - your current round reward diminishes with every refresh by 0.005%
Perks activation like the way Bitminter is doing it should suffice.
Here's what Bitminter is doing.
1.5% donation to activate instant payout.
0.5% donation to activate API.