
Both my two, my main one a breed (hound) prone to GDV (Bloat) are fed two meals a day, splitting the daily amount into two - they have breakfast around 7 am, and the second meal no later than 5 pm to allow it to be at least partially digested before bedtime. I have always fed our main breed adults two meals a day, be even still, have had 4 cases of GDV over the years.
With our Whippet, who is now 6 (where have the years gone), she doesn't eat very much in terms of the size of her meals these days but what she does have gets eaten up quickly!! Up until recently they were both on the same Arden Grange Sensitive which my Basset needed and which I gave my Whippet as it was easier to have them on the same food. I've just switched them to Pooch and Company Tripe and rice which costs less, and comes in 15 kg bags which is a considerable saving since AG reduced their bags to 12 kg and kept the price the same!!
By a year, I'd suggest your Whippet only needs two meals a day, but again I'd keep him on 2 smaller meals. And I don't do free-feeding - always impossible with numbers!!
Rather than ask you vet for advice, unless he happens to be familiar with the Whippet specificaly, I'd ask his breeder who should know what works for the breed, and her bloodlines. And always remember not to feed for an hour after exercise, and not exercise for 2 after a meal. To allow the system to rest and hopefully avoid the risk of Bloat. Much as we had one we found surrounded by white froth in his crate at 7 am, before breakfast or exercise. What caused that I have no idea - happily he did survive, minus his spleen which had ruptured. He was 8 at the time.