My children's UA accounts show transfers from their CO accounts on March 4. Does this mean that their UA miles will not expire 18 months from March 4, if there is no other activity? Or does the transfer not count as account activity, so they might expire sooner?

I'm asking here because: (1) I couldn't find an expiration date listed in their accounts, and (2) three calls to UA resulted in a 30-minute hold, a disconnection, and a "call back later" message and then disconnection.