There are butyl tubes and latex tubes - one leaks more slowly than the other, I don't remember which. Checking your tire pressure every 3 days or at least once per week is recommended. If you let out pressure between rides, well, you get more arm exercise before each ride. But it's really unnecessary. Even leaving your bike in a hot car is unlikely to blow the tubes unless you normally run your tires within 10% of the maximum rating for your tire. In the ideal gas law, P is linear with T, so a temperature change from 70F to 120F is only a 10% increase (convert T to Kelvin).