We have no transmission rates for hsv1. It hasn't been studied like hsv2 has.
Does the partner with hsv1 have it orally or genitally?
Has the person without hsv1 ever been tested or are they assuming? The hsv1 IgG blood test misses 30% of infections, and the vast majority of people who have hsv1 orally never get symptoms.
After 50, depending on your age, up to about 80% of the population has hsv1. The older you are, the more likely it is that you have it. Under 50, about 67% of the population has it, globally, again with a higher chance the older you are.
You are asking about condoms and medication, so I'm assuming someone has it genitally. If the partner with it genitally has had it for more than 2 years, they are shedding about 4 days a year outside of symptoms.
At over 50, there is no way I'd ever let hsv1 be a determining factor in a relationship. If I said no to this partner, the next one would be just as likely to have it, and just not know it, or as likely to have a false negative on a blood test.
Good relationships are way harder to find than herpes is.