H1B Cap exempt - Till when

[sudeep.vaidya]

I received my H1B in 2015 lottery, but haven't been able to travel yet to the US. I've got my H1B stamped though and it has a date of June 2018 as Expiry date on it.

If I'm unable to travel by June 2018, what happens to the H1B ?

For how many years since approval (2015) does the Visa allow me to apply in Cap-exempt and I need not go through the lottery ?

[pontevecchio]

Look for a H1 sponsor if you want. You would normally have a total of 6 years in H1 status until such time the laws are changed.  The visa stamp would possibly mean you were cap counted once and hence are entitled to a total of 6 years in H1 status. I will let you look up what H1 status means. No time limit.