I meant instead of running heartbeat() on every user canister, you’d have the same functionality but run it from a remote_heartbeat() function. Then, using my example above, you’d “register” each client-canister with a remote_heartbeat at say 30 minutes. Or whatever interval you need.
Then the main heartbeat canister will call each client canister with remote_heartbeat() at the set interval. This way you have all the implementation canister-side and also can use a much cheaper version of heartbeat - you only pay for heartbeat on one main canister, and for each remote_heartbeat() you just pay what you need (e.g. once every 30 minutes)