imho: Refill during a 3 months period. But I would suggest you simply buy a new simcard! Other plans are much more interesting, as they contain cheaper data plans and / or international rates (i.E.: Blauworld: http://www.blauworld.de/tariff 49ct / MB or 7,90 EUR for 1 month flatrate internet + 5ct/Min to USA and european destinations http://www.blauworld.de/cms/blauworl...preisliste.pdf)