請教大牛們：我應該保留哪個term life insurance?

目前有三個terms:

1. 500K, Brighthouse (former MetLife), till age 67, $750/yr, conversion period end by the end of policy, accelerated benefits rider
2. 500K, Amica, till age 75, $850/yr. conversion period end in my age 55. Terminal Illness Rider ( same as accelerated benefit rider I think)
3. 1.5 times salary term insurance through employer, $500/ yr, can convert at the end of employment 

家有小學娃一枚. 3感覺很虧，準備cancel. 1/2隻想保留一個，本來想著2可以保到75歲那就cancel 1, 但後來有注意到1可以有更長的conversion period 而且貌似保險公司更好。這個conversion privilege 重要嗎？一般人會用得到嗎？是不是說像得了絕症就會考慮convert 所以conversion period長一些好？到底是保留哪個term 呢？謝謝。