do duty as (verb) serve: suffice; do the work of
Sinonime: at intervals, at random, at times, every so often, from time to time, hardly, infrequently, irregularly, now and again, on occasion, once in a blue moon, once in a while, once or twice, periodically,
seldom, sometimes, sporadically, uncommonly
Antonime: always,
constantly,
frequently,
regularly, steadily,
usually