I regularly travel to Europe (Germany, Poland, France, Switzerland). Every time that I arrive in a country, I buy a cheap prepaid SIM card. The problem is that all these cheap SIMs have a short inactive life, due to their pay-as-you-go nature. For example, most of them will die after 3 months of inactivity, and it is almost impossible to reactivate them.
Is it possible to buy a (probably expensive) SIM, which work for a long time regardless of its activity? I wish to have permanent mobile numbers in certain European countries.
For instance, I travel approximately once a year to Europe. Every time, I should email my friends that next week I will be in Germany, and after arrival I will text you my new number to reach me. I wish to have a permanent German mobile number, as I can email them that next week I will be in Germany and you can reach me at my German number (which is already in your phonebook).