Does the tourist visa get cancelled if applicant does not enter to USA immediately?

[karthick.cit]

My parents B1/B2 Visa (Tourist - Multiple entry) got approved on 2015. And, my parents are planning to visit USA this year.
Does the tourist visa get cancelled if applicant does not enter to USA immediately after the approval?
My understanding is that isa is approved for 10 years and applicant can enter to USA within given 10 years any time?
can anyone please confirm?

[Tezza]

My parents B1/B2 Visa (Tourist - Multiple entry) got approved on 2015. And, my parents are planning to visit USA this year.
Does the tourist visa get cancelled if applicant does not enter to USA immediately after the approval?
My understanding is that isa is approved for 10 years and applicant can enter to USA within given 10 years any time?
can anyone please confirm?

Generally yes, the visas are granted for a 10 year period, so you can go at any time. Some of them are granted for shorter periods, you will have to check the visa itself and confirm the specifics.