Only necessary if you are having problems with excessive or uneven wear on your front tyres. The rear suspension is probably not adjustable, and "toe-in" is the only easily adjustable setting on the front wheels.
Provided you haven't run into anything hard, the alignment shouldn't be too bad, but most people would suggest having it looked at after 8 years. Suspension components do wear, and during alignment, a reputable operator will check it out for you, and will also be able to suggest a suitable toe-in. Maybe $40 cost, or free with a new set of tyres?
I've only had my cars aligned every now and then. One car was delivered with poor alignment, and another had a minor impact to a rear wheel in traffic. Once got a free alignment with a set of tyres.
The front wheels should be parallel (or nearly so) when they are on the road. A small amount of toe-in is often applied (e.g. 2 mm). It is difficult to measure the alignment without special equipment. It is also necessary to check for bent wheels before carrying out the alignment.
I have seen it suggested that you can make the measurements yourself, but it hardly seems worthwhile, considering the accuracy required. Of course, with the car on the road (not hoisted) the car body/engine will prevent direct measurement in most cases. Are your tyres wearing unevenly?
Wheel alignment shops clamp brackets to each wheel, and these are used to take measurements, commonly using mirrors and laser beams. There are adjusting lock-nuts on the front steering arms to make toe-in adjustments, and care need to be taken to end up with the steering wheel in the "straight-ahead" position.