It ranges between 80 and 300 days (up to 2 years) depending on ambient conditions and the nutrient value of the food substrate.
Adults come out as soon as April and are active at dusk. Females lay their eggs in small cracks in wood vessels (more than 0.05 mm in diameter), provided that they are dry, intact and have a very high starch content. Average fecundity is about 20 eggs, laid in small bunches of 2 to 6. The eggs are translucent and round, 1 mm in diameter,  they incubate for 1 or 2 weeks (depending on ambient thermo-hygrometric factors) and then new-born larvae hatch. Larval development varies, as larvae remain inactive in winter and when ambient conditions are not favourable. New-born larvae live in 1- to 3-mm wide galleries that they bore along the wood grain, which differentiates them from furniture and deathwatch beetles (cf. Anobium punctatum and Xestobium rufovillosum fact-sheets, for example), whose galleries are bored in all directions.
Galleries are often blocked by bore-dust with a very fine and very volatile aspect (“meal flower” aspect). Bore-dust can sometimes be seen on the outside, which is a good indicator of that dreadful pest’s presence. Once their development is over, larvae turn into nymphs and the nymphal stage lasts between 2 and 3 weeks.
When adults are formed, they settle in small cells quite close to the surface where they stay for about 4 days, and then they bore a hole to the outside to break free and take flight. It should be noted that Lyctus brunneus exit holes are round, like those of furniture and deathwatch beetles.
Adults’ emergence occurs between April and September, there can be 2 or 3 generations per year in heated places, at temperatures ranging between 17 and 23°C, and humidity rates between 40 and 60% outside the wood and 14% inside the wood (below 7% humidity rate, larvae cannot develop).
Male adults live about 2 months, females about 4 months.

Lyctus  brunneus more particularly infest floorings, wood panelling, plinths, door or window frames, furniture and all kinds of worked woods or wooden objects through which their larvae bore countless galleries that weaken the wood and sometimes cause it to actually crumble down.
When their flight holes are spotted on the surface, it is usually too late to do anything for the infested material is then nearly completely hollowed out.
They are particularly fond of the soft parts (sapwood) of deciduous trees such as oak, chestnut-tree, ash, walnut-tree, elm, willow, cherry-tree, but more rarely beech or poplar.
Starch-rich tropical woods (abachi, koto, okume, limba, lomba, ramin, along with bamboo, acacia, mahogany…) can be destroyed by powder post beetles, as well as plywood, which is often made from the woods cited above.
It is important to note that wood from resiniferous trees is never infested by Lyctus  brunneus (but it can be infested by other insects (cf. Hylotrupes bajulus fact-sheet, for example)).

Lyctus brunneus is now distributed worldwide due to the flourishing international wood trade.