I am seldom "surprised." There are SO many indications that orgasm/ejaculation is imminent. But when I DO get surprised ?? I LOVE it! Especially when I'm "surprised" with an unusually LARGE load of cum.
thats why you hold his head and control your cock sucker, feed him your seed and he has to know how lucky he is to get your load of cum, hold his head on my meat as it pumps him that seed, and make him swallow it down.
It's common that the only warning you get is when his first jet hits the back of your throat and your mouth fills with the taste of his cum. I love it that way. Hold the back of my head and unload.