[Bossman]

Actually, in OP's situation, spending a few weeks in each of those countries and needing to make and cheap calls and receive free calls, a country-specific sim is the best option. As already posted, there are several ways to keep those sims going if you need to. My virgin UK sim is at least 6 years old, and I have only used it within UK twice in those years. I have kept it active/going my one of the ways already mentioned. Also, the so-called global sims do expire as well if they are not used within a certain period.