I have a different experience with the CE light. Mine kept coming on every couple of months and staying on (I have a '98 and the logic for turning off the CEL is different in '99 than it is in '98 cars). The first few times the dealer gave me the gas cap explanation. Even replaced mine with the "older" style from an 850. No help. CEL kept coming on as before. The dealer then started replacing parts (under warranty). Charcoal canisters, check valves, rollover valves, you name it, I have had at least two replaced. No difference in CEL behaviour. I got fed up and wrote a letter to the service manager, who got personally involved and finally, started to work the problem, instead of blindly replacing parts. The whole time the codes that were stored were 611 and 612, which are fine and gross vapor leak in the vapor recovery system - classic "gas cap" codes. To make a long story even longer, they have determined that my gas tank was defective. After ordering a new gas tank, they figured out that the superceded gas tank (new design) did not fit, so they had to locate an old-style new tank. When that arrived it turned out that my original tank was missing some sort of restricter, a tiny nylon washer-like part that sits in one of the numerous hoses coming out of that gas tank. Put that restrictor in and... It's been just over a year now with no "gas cap" CEL. So, the moral of the story is that the gas caps maybe just fine in these cars and the problem is elsewhere, like a missing restrictor in the gas tank. But, since the codes that the ECU throws are the ones that suggest the gas caps, most dealers just blame the operator.

I did end up buying an OBD-II scanner though to be able to clear the CEL so I can pass inspection once my car is out of warranty and all the CEL episodes are on my nickel.

Good luck.
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Vladimir. 1998 S70. Base, 5-speed manual.