Humm, that's a very good question AI.

I can't offer any hard facts to support or disprove your hypothisis but my opinion would have to be no. Computer hardware does not "break in" the same way a car engine would per say. There are no moving parts that get smoother over time. Only electical connections that if anything break down over time or perform differently with various voltages / amps.

The only explanation I could afford to offer in your situation would be that over time you might have installed a better driver or updated bios that would support a higher clock speed.

Again, I want to reiterate that this is only my opinion. I admit I have a some-what limited expierence in electronic engineering and could very much be way off base. I only offer my opionion from my past exp. in electronics and computers. I would welcome the insight anyone else could offer on this for my own benifit.