What are you setting your application pool memory limits to and are they shared with any other web application? This is typically the only instance where you will come across resets (Memory pool out of memory will recycle itself). Please see the system requirements
for Sitefinity 5x.
Have you checked out some of the solutions outlined below? I have Sitefinity 5.1 installed on Arvixe business class shared with 500Mb dedicated App_Pools for my blog which takes ~1200+ hits/day and I have not run into any performance related issues on the front or back end.
If you can give me some idea about your environment I'm sure we can get it running smooth for you.
In the mean time check out this post on keeping the site warm
and the links below about keeping your backend warm as well.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items