We are having a lot of problems with time taken for web pages to load (users say things like "browser crashed" but while that isn't true - we can see very slow times for some pages). We need to monitor loading times in some way which replicates what a browser does (in terms of multiple request/response).
I would suggest some third party tools that can be considered as best practices: perhaps external performance monitoring - which monitors your website from outside the firewall (through a true browser), that way you can identify errors, and at the same time, monitor the availability and performance of your website. Most importantly-- obtain an end users perspective (staging environment rather than production environment)
In addition, load testing prior to launch is also considered a best practice where you are able to test capacity and id bottlenecks.