You emailed me or left a voicemail and now you're wondering “That @$$#0!3! Why hasn't Rik got back to me?” If I'm busy I just may not have had a chance yet. So check out my current workload for yourself.
Under light workloads expect a response within a few days. I should be able to get back to you within a week under moderate workloads. But when my workload is heavy it could take a few weeks. Also check my schedule: I may be in a meeting or out of town.