The tetanus part probably lasts for much longer than 10 years in most people (cases of tetanus in people who received their primary series are vanishingly rare, and some countries don't even give boosters) [1]. But tetanus is kind of like rabies... you'd be crazy to mess around. Even a nonlethal case of tetanus is devastating. Thus, the recommendations tend to be quite conservative, and you should be too.

The aP part (acellular pertussis), on the other hand, actually doesn't last very long. The acellular vaccine unfortunately is just not as effective as the now-discontinued whole-cell vaccine. So even if you think the tetanus version isn't strictly necessary, get your booster for the pertussis portion....

[1] Hammarlund et al, "Durability of Vaccine-Induced Immunity Against Tetanus and Diphtheria Toxins: A Cross-sectional Analysis," Clinical Infectious Diseases 2016.