How many lights on a 15 amp breaker

Redoing the basement lighting circuit. Is there a code or general rule of thumb when it comes to how many lights can be put on a 15 amp circuit?

I am familiar with how to convert between watts and amps. And I know how to figure out how many 100 watt bulbs can be on simultaneously before blowing the breaker, but was curious what the pros do. Do I max it out since it is unlikely that all the lights will be on at the same time OR leave 20% of the available 15 amps unused???

Thanks!