Perhaps the following will answer your questions
This is due to the LocationSensor reporting a slightly different set of coordinates. Read about Accuracy in * Using the Location Sensor . So why is it not providing an address? Read Using the Location Sensor. The gps is not as precise as you think it is.
No, whether you get a Street address depends on whether Google has the coordinates reported in the data base. It is not request limited.
If you want to know the CurrentAddress of your present location, yes of course.
Only if you want to know where you have been.
Read this material if you haven't already Barry (and consider doing the tutorial experiments) and you will have a good understanding on why you get the results you see.
Perhaps you live downtown in a fairly large city where housing/apartments are dense or in an building that obscures your view of the positional satellites. Either circumstance will give you a good chance of No address available.
If you go outside, you can probably get an address.
This could happen if the latitude and longitude reported are exactly the same and the device thinks it does not have an address match with those specific coordinates. Walk outside, see what happens.
However, the good news: you will ALWAYS get your latitude and longitude. 
Did this help?
Would you like to know more? Discussions of CurrentAddress issues.
A footnote: Your device gets the CurrentAddress from Google's Cloud. The default CurrentAddress is No Address Available. If your device does not have a WIFI or data(network) connection, you will probably see No Address Available.