Contracts till end of current season

Right, I've looked all over and haven't seen anything answering this particular question. My youth players are on 55 p/w and have 18 months remaining on their contract. I could offer them a contract now (mid-September) until the end of the season but they'd need to have their wage increased to at least 100 p/w thus negating any financial gains I could be making. :o I know. Last year, I recall offering a youngster a contract in mid-February till the end of the season fwiw.

I'm wondering if anybody knows how late in the season it is possible to offer a short-term contract? I suspect it's till the end of February but was wondering if someone could give me a definite answer...