Temps will stabalise fairly quickly, Id expect 4 or 5 minutes to be enough. It wont heat up your graphics card, that's what furmark is for.
Ideally test with side on and off. If airflow in your case is good, it'll be cooler with the side on. If airflow is bad (probable), it'll be cooler with the side off. The difference in load temps with and without panel therefore tells us things about your cooling arrangement.
I'm not sure what the thermal limit for your processor is, but it's quite possible it's 60 degrees. Intel ones tend to be rated to 70, but my only amd one is rated up to 60 degrees. Intel burn test might not run on amd processors either, in which case prime 95/orthos is the answer (same program, different interface. orthos is a bit nicer).