I would give him another chance. You gave him a Christmas card with your number in it? Maybe he was super busy during the holidays and beginning of the new year; or it's also plausible that he is shy. Who knows why he didn't call right away, but he did call you... so you eventually got what you wanted, even if it was delayed. I think part of the problem is because now that social media and smart phones have taken over most of our lives, we expect an immediate response from someone we reach out to; and we assume that they are not interested if they don't respond right away. I'd give him a chance. If there's a spark, then see how things go. If you don't feel a good connection from him, then call it a loss and move on.
"Caring is not an advantage."