there is no right or wrong time to get another pet, you will know when the time is right, don't feel you are replacing the lost one , one does not replace another but it makes a new place of its own.
Four years ago I lost my beloved bengal cat to cancer. He was 12 years old. He was so bonded to me that when I left him alone he'd pull out his hair, I took him to the vet and the vet said it was just stress and to get him a kitten. I got him a siamese kitten, I used to joke that he left me for "another woman". When he passed the siamese was devastated, she'd look for him constantly and cry, and even try to get outside to look for him. The Christmas before he passed my daughter had a large oil painting done of him for me, I have it on the wall but couldn't bear to look at it so I turned it around. That year for mother's day my daughter and son in law bought me another bengal kitten, he wasn't born yet but they had put a deposit on him and I got pick of the litter. The siamese was overjoyed to have another kitten to love, as time went on I turned the picture around so I could look at him once again. This time with fond memories of him and the time we had together. This year for Christmas that same daughter bought me another bengal kitten, this one is a snow. At first the siamese didn't like her but after a few days everyone adjusted to her being here and they are all happy and run around playing together. I still have his picture hanging up and I like to think he's watching over the others. Will you get over the loss? Not entirely, you will always think of the one you lost but having another will help lessen the grief, Think of it this way, he's physically gone but he lives on in your heart and memories. He'll always be with you.
He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion"