What happens to wine when...?

[Deputy]

...you can't drink the whole bottle within two days.

I've been experimenting with wine as of late and I've found that when I open a bottle, close it up, and put it in the fridge (ie the bottle of Naked Grape Shiraz I'm finishing up right now), it tends to get a lot more...tart the next time I open it. I opened this bottle...hmm...two or three nights ago, I think. It's fairly tangy now.

Another question...another "how old is too old" question. We have a bottle of 2002 J.P. Chenet Chardonnay taken from a cruise ship a year or two ago. It's been stored mostly upright in the cupboard above the fridge, which probably stays an average of about 70* (basement suite).

Is the best bet just to open it and hope for the best, now?

Thanks!