I have noticed how often AB becomes unavailable for a short period during the early evening. I am convinced they restart SQL Server regularly, or even reboot the entire system. Bloody Microsoft, the standard solution is to reboot. I had a Unix system running for 3 years continuously without reboot, the only thing breaking the uptime run being the installation of new hardware.
I haven't noticed slow-downs in the evenings but I do regularly have trouble with AB at around 1pm every afternoon.Sometimes the site just won't load at that time.
Got to agree with you there, Whiffey... if you had a car and it kept *dropping out* you would not be too impressed at having to turn off the engine and starting it up again. I ran a couple of Sun workstations (also on Unix) continually for 5 years with no reboots ever !