I agree with the previous posters that for sous vide in a water bath, your goal is just to remove enough air so that when you are immersing your food it rests in the water and doesn't float to the top. The danger of going too far and too long in the vacuum sealer is that when you've lowered the pressure too much liquids will boil at room temperature. If you are sealing a nice cut of meat and hold it in the vacuum too long, the liquid in the beef will boil and change the texture, generally not in a desirable way. For fruits and vegetables, you may be wishing to get that texture change, so knowing the boiling point is key. You mentioned you got the sealer for experimentation, so why not spend some time experimenting with how it works before you try experimenting with recipes? Try sealing bags of water at different temperatures to see what you can get away with before they begin to boil. Use this as your guide. Learn how long you can go before the pressure results in refrigerated liquid boiling. Buy some cheap cuts of meet, say chicken legs, and see how long you can go before you've "cooked" them in the chamber (and throw them away; please don't taste them even if the boiling juices made them less pink). You can even use dried beans or uncooked rice (or things which aren't edible, like spoons and forks) to get a feel for how long you need to seal to remove enough air for full immersion in water. I regularly use my vacuum to package food that I've cooked for freezing, and this experimentation has been very helpful in my understanding how long I need to wait for things to cool down before I can seal the food after it's been prepared - do I need to put it in the fridge overnight, or will a few ten minute rests surrounded with cold water in the sink be enough? Can I go for 20 seconds before boiling a bag of 80F degree chili, or is it better to wait until the next morning when it's at 38F? Do I need to go longer for food which might trap air, and how long can I go when sealing dry ingredients where the risk of boiling is far less? Where should I place food in the bag to allow for air to easily escape? I find myself disappointed if I'm not minimizing the freezer burn as much as I thought I could when taking things out of the freezer. Spending thirty minutes with the vaccum sealer, thirty bags to potentially waste, and lots of objects has resulted in my learning the sealer like I would a new pot or pan. As you are spending time learning your vaccuum, be sure to vaccuum seal ice cubes. They'll go from solid to liquid, and then when the pressure rushes back in it'll return to a solid state immediately. Very cool. I've had a blast with my chamber. No regrets whatsoever in buying it. My wife thought I was crazy to purchase it due to the high price and size, but she's more than willing to assist now that she understands the options it gives us. My gut tells me you can ignore the explicit directions to "seal to 95%" and instead, just get enough air out so you aren't left with a bag floating in water or the texture you want when you are simply playing with pressure. Learn the timing if your machine through experience and you'll be in great shape to consistently get the pressure you need without wasting bags or destroying the texture of the food you are sealing.
