Yes they can. I'm not convinced they're worth the hassle though. They seem to only make a positive difference on cheap wine which would go bad overnight. Most good wines will hold up to and many will even improve over a day or two. Unless your thermostat is set to <18, stick em in the fridge. I had a vacuum sealer and found that using it caused a loss of flavor in wines compared to the same bottle just stoppered with a cork. I've had better luck with nitrogen preservation but what I most like to save are pinots and even the nitrogen can't keep them for more than 4 days or so.