You should check your emails according to your needs or acccessibility,if you are expecting some 

certain emails then it would be ideal for you to check it like four times daily but if the email is not 

that important then you can be checking it maybe thrice in a week,but checking emails daily 

is a good routine that should be practiced because you never know when an important 

email will enter your email box so that is why it is good to frequently check our emails..