I was just able to verify that the 180 day minimum for unlocking a Cricket locked phone is cumulative of any time on any account active on Cricket, i.e. the policy is not that the phone has to have been on your own Cricket account for 180 days. In fact, if the phone was active for 180 days on someone else's account but was not unlocked, you can put a Cricket SIM from your account into the phone and get the phone unlocked the next day.
Recently I tested by hypothesis when I bought a cheap LG Harmony locked to Cricket that I knew had been active for the requisite 180 days - the seller said in his ad description that he put the phone in a drawer after using it on Cricket for a year. Before buying it, I asked the buyer to confirm that he never requested an unlock and never used the phone on another carrier. I got the phone yesterday, and in the evening I swapped my wife's Cricket SIM into the Harmony and let the phone sit on standby overnight. I requested an unlock code this morning and got one, and the code worked.