I too purchased a wind up radio from Tesco a few years ago to take on my travels. I agree, it takes forever to wind it up to any acceptable level. It might be an OK idea if there is absolutely no alternative but if I were to want a radio again for travelling I'd just buy one that takes batteries. The batteries can be bought very cheap in advance of your trip and they take up no room in your luggage.
Whether the wind up option is suitable I suppose depends where you're going. Are you really likely to be miles from civilisation for an extended period? Or is your interest based on the 'green' credentials of such a device?
"Life is too short to drink cheap wine!"