Hi broomfieldbrc,
This is generally not an issue with our plugin and if it’s working fine with the free version, installing PRO is not going to make that much of a different unless you’re adding tons of recurring events. But this could be a problem in any case where you’re adding tons of posts, not just with our plugin.
I would say to test things out in the way you need to use the plugin. Ideally, setup a development instance of the website and test out the scenarios with how you want or need to use the plugin and see how it performs. If you’re running into issues, we may be able to help but sometimes it’s out of our control (web hosting, conflicts with theme or other plugins, etc.)
3.0 definitely offers improvements in a number of areas, including overall performance but again, it’s going to depend on your specific needs and your specific configuration and you will never know until you actually try it out. We’d be happy to send you a copy of the 3.0 beta if you’re interested. Just email pro [at] tri [dot] be with a request.
Does that help?