I’ve noticed too. Peak frequency used to be about every 4-6 minutes on the 39 but they’ve cut it back a lot due to driver shortages. Even with the reduced schedule though, they don’t have enough drivers to run the reduced schedule so some trips are canceled minutes before they’re supposed to run, leaving bigger gaps between buses.

Further, they don’t have enough bus dispatch staff, so operators often leave the terminal before or after they’re supposed to. This is further compounded by the fact that most of the 39’s route runs on Centre and South Sts, which are congested for large stretches of the day. That’s hard to plan around. This part has gotten a little better with the new bus lanes on Huntington, but the 39 still gets caught in a lot of traffic, making headways less reliable.