I totally disagree with hacking and slashing a NES to make it "work" without pushing the cart down, or by making the ZIF so tight you need the jaws of life to get the game out, but hey, I guess that's just me.
Keep your games clean and keep your system clean and you'll have a well running NES, says I.
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My mantra, as worded by SamSpade on 06/12/12:
I don't resell to fund my collection, I don't treat this hobby like a second job, I don't care if my collection is worth ten bucks or ten thousand because I never plan on selling it. Seriously, what does the value have to do with anything if you never plan on selling? Speculation doesn't mean jack shit to me at this point, I just want to play my nes games...