Does the oleophobic effect of the iPhone screen wear off over time?

Unlike predecessors, the iPhone 4 has a screen that is more resistant to smears and smudges.

Is this a property of the glass itself, or is it a coating that will wear off over time? If it wears off, how long does that take?

Update: Some answers address cleaning the screen. I've never cleaned by phone except by wiping it across my shirt or pants-leg.

I've had an iPhone 4 since the day it came out. After the first year or so the oleophobic property has completely gone: it's now no different to my old iPhone 3G screen in terms of finger smears. I've never cleaned it with any sort of chemical agent but I've also never kept it in a case that covers the screen, and it spends a lot of time in my jeans pocket. So the answer is yes, under some conditions it certainly does wear off over time. Your mileage may vary, of course: kept in a case, or carried in a bag or purse where the screen doesn't get rubbed, it should last much longer.

Unfortunately, yes, the coating does wear off over time. Apple has this to say:

Please note that the ability of this coating to repel oil will diminish over time with normal usage, and that rubbing the screen with an abrasive material will further diminish its effect and may scratch your screen. —Apple

However, and this is good news, there are aftermarket alternatives to re-apply an oleophobic coating. Aculon is in the business of applying lipophobic protection (among other types) to a range of devices. I'm not sure how well they work or how much they run but a solution does indeed exist.

And for the curious bunch among you, here's what Bill Nye (The Science Guy) says on how the substance works:

The new 3GS iPhone has a coating that helps you leave no, well hardly any, prints—fingerprints. The glass screen is coated with a polymer, a plastic that human skin oil doesn't adhere to very well. People in the chemical bonding business like to call the finished surface "oleophobic."

Such a lovely Greek cognate may sound like it means "afraid of oil." And, it does, but it also connotes (or carries with) "aversion" or "not-like-to-be-around-tivity," if I may. Instead of sticking to the bonded-plastic surface of your new phone, the oil from you fingers or cheekbone or tip of your nose stays more or less together as its own smooshed droplet.

The Applers were able to do this by bonding this oleophobic polymer to glass. The polymer is an organic (from organisms) compound, carbon-based. The glass is nominally inorganic, silicon-based… solid rock. The trick is getting the one to stick to the other. Although it is nominally proprietary, this is probably done with a third molecule that sticks to silicon on one side and to carbon-based polymers on the other side. Chemical engineers get it to stay stuck by inducing compounds to diffuse or "inter-penetrate" into the polymer. The intermediate chemical is a "silane," a molecule that has silicon and alkanes (chains of carbon atoms).

If you'd like—and I hope you will—take a moment and think about droplets, like water droplets, on a surface. Deep in the droplet, water molecules stick to each other. On the surface though, they stick to each other as well, but they also have to opportunity to stick or not to stick to the surface they're resting on. When they stick, say to the nylon fibers in a bikini strap, the swimsuit feels wet (or so I'm told). When they don't stick to the surface they're resting on, they bead up, like in the car wax commercials.

Well, the polymer that the 3GS iPhone screen is coated with doesn't let the oil of your skin stick to it very much. So, you don't leave fingerprints. The key is in the intermediate compounds, the silanes that hold the plastic to the glass.

So grab a hold of one, and for a change, watch almost nothing happen. It's chemistry. —Gizmodo

I have owned an iPhone 3GS for one whole year and then an iPhone 4 for a year and a half. In both cases, the oleophobic coating has never rubbed off, and I use my iPhones a lot!

I would say that this coating is very well bonded to the glass.

It depends if you clean the screen of the phone with strong alcoholic solutions. Some alcoholic solutions wear off the Oleo-phobic coating.