If your downloaded block count is not up to the networks current value (roughly 67,000 right now, a new one every 7 minutes), then your client is still downloading and verifying blocks. That takes a little hard drive each time it seems. Once it is caught up that little bit of hard drive usage would be only every 7 minutes.
It is not memory intensive and currently the database takes only 58 megabytes after being a year old now I believe.