Thanks for posting your query.
As you rightly pointed out the HIV
symptoms may likely to occur after years of the last risky contact by which time he may likely to spread the disease to others.
He must have the blood screening for HIV preferably after 12 weeks. If you want to know his status still early you have to go for HIV DNA PCR test which will become positive within 3-4 weeks after the risky contact.
Get him checked and till then have protected sex.