Will you be traveling within one region or multiple, e.g. Americas, Europe, Asia, etc.? I'm not sure about Europe but in North America, between US/Mexico/Canada, I didn't need to purchase separate SIMs because Verizon gave me service in all three countries. Traveling in Asia now, I just find it easier to purchase local SIMs and have a local number. The problem you run into with not having a local number, especially if you're staying for months at a time, is that local people and business cannot contact you. When it comes to lodging, metro cards, bike shares, reservations, etc., a local number just makes things smoother. For contact with family back home, I use message apps or an Internet phone service like Google Voice. There are phones with dual (triple?) SIM slots, so that could be another way to go.