the only limits are what my single server setup will support - if there's heavy traffic responses will take longer. I've only had to throttle a couple of IP addresses over the years when they've been totally flooding the service with parallel requests and I've been unable to contact the owners. Most users have been good citizens and not hit it faster than it can respond. If you want the best performance, I recommend downloading the VM or setting up your own EC2 box from an AMI, that way you'll have it all to yourself!
Thanks for asking though, I appreciate your thoughtfulness, and let me know how it goes.