Note that threads != processes. Threads are fairly cheap resource-wise (but not free). Of course if your plugin gets a separate process when it executes, but the sleep itself (when necessary) is not a big deal as it's inside the daemon process that is running anyway (also, even in those cases there is one extra thread per event -> we only schedule the next one).

Just a caveat, it's not just precision, but speed, too. If it's a sleeper thread, the 'payload' gets executed as quickly as possible (if it's native Qt code -> instantly). If we start from cron it always needs to load libs and startup and whatnot regardless of how complex the plugin is, and would feel a bit like trackerd ('what the hell is he doing with 100% cpu in the background again' syndrome). Don't forget - I'm scheduling, not polling !