Life metrics for v-brake pads (time to replace, time to change)
It's difficult to give a general estimate on how often brake pads should be replaced, as conditions vary. (Including how often you ride, temperature, humidity, do you store your bike in direct sunlight, how old the brakes are, etc.) If it looks worn, replace it.

Adjusting brake tension via the screw nuts on the handlebars is the best way to make adjustments. As brakes wear down with use, you will need to make these adjustments to compensate. Needing to do this ever month or two seems within the normal range for how often you use your bike. 

Another factor to keep in mind is that cables will stretch with use. If the screw nuts on the handlebars are at their limit, you will need to loosen the nut holding the cable at the brake to adjust the cable. (When you make this adjustment, make sure to reset the screw nuts on the handlebar).

Your recently purchased brake pads seem fine. I've found that a manufacture will include the housing even if it's not needed. Just be sure to toe-in your brakes slightly, and reset the handlebar screw nuts (and cables) as needed.