You asked

How often should I get my eyes tested?

It is vital for adults of any age to have regular eye examinations to check for any problems that may occur. Regular eye exams are critical for detecting:
For an adult, under the age of 40, that has no history of eye disease and has good vision then an eye exam every two to three years will suffice.
After the age of 40, an eye exam every 18 months is generally a good rule to follow.
At approximately 60 years of age, annual eye examinations are recommended. 

More questions

Children's glasses are subjected to a lot of 'wear and tear', follow our stpes to ensure your child gets the most out of their glasses.
Common eye complaints for children and teens include myopia, hyperopia and astigmatism.
Read more about what is involved in a comprehensive eye exam.
Teenage bodies are constantly growing and changing and during this time, eyesight is liable to change seemingly overnight.
A scratched cornea can be painful but is usually not serious.
Selecting the right pair of glasses for your child is important as they need to be durable but your child also needs to be happy to wear them. 
Children's eyes are sensitive so it is vital to protect them from the sun's harmful rays.
Your young child can have their eyes tested even if they can't read
Regular eye exams are essential in order to monitor your child's eyesight.
There are some signs to watch out for if you think your child may have a vision problem.