return ticket at the port of entry

[knvdssr]

My mother is coming to USA next week.
Can we buy the return ticket exactly for 6 months? What could be the issues if we take the return tickets exaclty on the end of 6 months?
If we buy the ticket for 6 months how can we be sure that she will get 6 months at the port of entry?
In order not to take chances till the last date, if we take the return ticket for 5 months 2 weeks, will they give visa for 6 months at the port of entry. How may days before is sugessted?

Thanks in advance

[Murali]

Length of teturn ticket alone does not gurantee, the I94 length, It also depends on questions answers by the officer at POE. But in most of the cases the I94 length is 6 months.