The Pro version you purchased will work for a lifetime, but you can only update it for the alloted time depending plan you bought(6 months or 1 year). After that you can't update it without repurchasing. There's probably a newer version out and that's why it's asking you to update it. You'll just have to ignore it.

Make sure you back up your Pro installer to a disc or some other safe place. In case you lose it for some reason(system crash, reformatting, ect). So you'll be able to reinstall it without having to repurchase it.

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