I switch telephone providers every year or so. As MNP (and LNP for that matter) is not available here, I have to switch actual telephone numbers alongside. In spite of that, I try to keep all of my old numbers – gotta like to stay in touch.
Generally that is attainable (however cumbersome and sometimes expensive) by setting up all the “old” numbers to forward calls to my currently active one. In luckier parts of the world, MNP addresses most of the issues. In addition, a new trend – specialized companies providing an attractive service “one phone number for life” – has been put on rails.
On the face of it, the idea seems very alluring. Probably everybody has gone at least once in his or her life through the horrors of a telephone number change by force.