The risk for receiving oral is gonorrhea, chlamydia, syphilis and maybe genital herpes type 1, if you don't already have oral herpes type 1.
It's a lot lower risk than unprotected vaginal or anal sex, but there is still a risk.
Yes, most people have oral for just a min or so, which really doesn't warrant the anxiety they have for it. Most experts don't think an unprotected oral encounter to completion even warrants testing, no matter how long it lasts, unless you get symptoms.
If you have a regular partner you are concerned about, then test to move beyond it. Otherwise, no need to spend any time on it at all.