Both safelights (a DIY 635nm red LED unit, or a Thomas Duplex LPS unit) are always left on during the entire session. Both have had their filter packs custom augmented and have been carefully tested using pre-fogged Ilford MGIV RC (LEDs) and Kentmere Bromide FB Grade #3 (Duplex). The LEDs out to 60 minutes, and the Duplex out to 30 minutes. Not a hint of fog in either test. Or in actual prints made under the same safelight conditions.
The room is comfortably bright in both cases. With the Duplex vanes open all the way, however, it's actually uncomfortably bright and makes easel focusing difficult or impossible. To see the image on the easel I must close the vanes. With open vanes my sense is that the Duplex is about the same as having a 40-watt conventional light bulb switched on in the room.