I open all the decks I buy. However, I've gotten into the habit of only unsealing/cutting the top portion of the cellophane since I want to minimize the wear on the tuck cases while still being able to enjoy the cards.
Beware that over time the cellophane has a tendency to shrink, putting pressure on the tuck box. In your case, it would possibly damage the box, but would likely split before it got to the point of warping the cards inside - the side edge of the cellophane isn't as strongly secured once the top portion has been removed. The only time I save the cellophane is if the box has an open window in the back, like many casino decks, or if the cellophane has a unique feature, like the hologram on the Bicycle Be@rbrick or the sticker on the Bicycle Hanshin Tigers.
I own just over four hundred different deck designs and more than a thousand individual decks. Most decks I get in twos, sometimes threes, leaving one opened for use. But if I only have one, I open it! I get my pleasure from seeing, feeling and handling the cards, not staring at the sealed box. I've said before on one of these topics that I equate it to purchasing a rare painting or sculpture and displaying it while it's still in the crate it was shipped in, never to be opened. I never worry about future value much, because I don't want to get rid of my cards until I'm just too old to play any more. The decks I buy in larger quantities are either very common decks for use in magic, very cheap decks that I got as a bargain, or decks that I intend to use as "trading fodder" - currency to trade with other collectors to get new, unique decks I don't own or want more of.
I own just a handful of vintage decks, most of which are bridge-sized airline decks from the '70s/'80s. As much as I'd love to own some more vintage decks, my hobby is expensive enough as it is! But I certainly wouldn't turn a good one down if it happened to come my way in a trade...