365 ME Saudi Visa Validity to Arrive in Saudi Arabia

Dear Gurus,
I've applied 1 year ME Visit Visa for my parents and it was stamped on 14th January 2019.

My Question is how much time do they've to fly to Saudi ?

- Can they come anytime in 365 days ?

Because I've booked them flight for 15th march 2019  ( almost after 60 days of visa stamped in passport )

Regards,
-Bash

They can come in at any time during the visa validity period.  On first entry, they will be photographed and fingerprinted at point of entry and the officer will write, by hand, a number in Arabic on their passport - this is the border number.  Used for literally everything e.g. to get a SIM card in their name etc.