First, relax, and enjoy your PS3.
Your PS3 is designed to handle constant use as both a game and home theater system.
As far as dust is concerned, just keep the vents as clean as possible. I've heard of some people using a vacuum cleaner to suck the dust out (one way) but I just keep wiping mine down w/ a mild-damp cloth from time to time.
According to Sony's website.....(from the horse's mouth)
"It is important to maintain your PLAYSTATION 3 system by keeping the vents on the system free of dust. Because dust can accumulate in the vents of the PLAYSTATION 3 system, we recommend that you check the vents periodically (and clean them if necessary). After turning off your system and unplugging it from the electrical outlet, you may remove any accumulated dust with the hose attachment of your vacuum cleaner or with a small handheld vacuum."
...as far as the BD lens, Sony says....
"We do not recommend the use of any type of lens cleaner. Instead, we only recommend cleaning your discs using lint-free "CD wipes" found at your local software stores. When cleaning the discs, start at the innermost circle and wipe towards the edge in a straight line. We do not recommend wiping in a circular motion, as it may scratch on the disc."
My PS3 has been running just fine, so I would say just make a point to keep it clean and it will give you years of service.
Good luck!