One piece of advice that we learned is that if you have a large enough team and the product you are talking about is some kind of “impetus for quality, so people can test” the type of scenario, resist the desire to build it every time who something is checking something. It is likely to lower QA for a while and cause QA to be interrupted before you find out that people check stuff all day.
For the push to QA scenario, just send it every night if it detects changes.
For the “see if it builds” scenario, every hour is good (again, people often check the material too often in a decent-sized team to make instant assemblies worthwhile)