this is not a typical behavior - of any car.
with both sides going out frequently, I would be looking into electrical issues - most likely suspect: a bad ground related to the headlight circuit.
What condition are the connectors in? (the part the bulb plugs in to) do they show any corrosion, darkening (burning) or anything unusual? (note: there should be some dielectric grease in there - factory grease is kind of creamy in color)
When installing new bulbs - never, ever touch the actual bulb! oily residue from your hands will cause them to burn out faster.
Make sure the bulb is fully plugged in to the connector - partial connections can also cause early failure.
I know Sylvania Silverstar bulbs are prone to burning out.
I have had Sylvania Silverstars in my car for almost 5 years now & have yet to have one burn out, and I run my headlights nearly all the time (now watch, now that I have said that, one will go...darn Murphy)