How long does the wi-fi purchase last?

I bought 20 hours last year and only used a few, anyone know how long you have to use the time?

I have seen 6 months and 12 months, but as not on a site at present cannot log on to find the answer.

Also I suppose you cannot find out how much you have left over without being on site.

This will be the last time I purchase any time as its a

TOTAL RIP OFF

I believe its about time they chucked it in for free.

Anyway anybody know the answer to my question?

Ta