Does wine go off i you open i screw off top but put it back on...how long does it last?!

> Does wine go off if you open
Yes

> how long does it last?
Screwcaps will help it last longer than a straight re-cork, but your enemy (air) is already inside. In the fridge you can get 2 weeks, maybe a bit longer. The wine won't spoil in that time, it'll just taste flat and weak. It probably won't truly start to spoil for a month, but it won't be worth drinking.

If you're planning to drink it over the next week, store it in the fridge and you'll be fine.

I would suggest once opened keep it in fridge and use within a week, I do this and it still taste's fine.
You don't say whether the wine is red or white, if white it's ok to drink chilled, if red take it out of the fridge to acclimatise to room temperature.
Happy drinking.

Wine starts to oxidise as soon as it comes in contact with the air, but by and large a screw top bottle will last around 3-4 days (less if its in my house lol!).

I use one of these http://www.vacuvin.nl/Vacuum_Wine_Saver_… if I'm not going to be drinking it quickly, it does make it last a little longer.

wine starts to oxidize as soon as you open it... and will continue even after closing again

red wines can start tasting stale after a few days, and bad shortly after that
whites can usually last a week or so before starting to taste off

Once wine comes into contact with air, it changes. White wine will go off after half an hour or so. Red wine mellows with air contact, but it will taste stale after a few days - how many days depends on the wine.

i re-cork and drink the next day and its fine :)