Is it possible to get mono more than once?

Yes: Mono is caused by the ebv virus. Once a person catches ebv, it seems to stay in one's body, and can re-activate to cause mono-like symptoms more than once. Staying healthy & happy, eating a balanced diet, and getting reasonable exercise, etc... May help keep one's immune system in top shape, to keep the ebv virus suppressed. Occasionally, other germs can cause a "mono-like" illness.

Married to it: Mononucleosis caused by ebv ( epstein bar virus ) some times also by CMV ( cytomeglovirus ) once infected virus stays in the body rest of the life, so married to it and rarely get a divorce !