How does stand oil paint/linseed oil paint set?
Linseed based paints set by absorbing oxygen from the atmosphere and with natural UV light. Therefore painting new joinery in a workshop with no access to natural light will slow down the curing rate dramatically.
Painting timber externally in the winter will also extend curing times as daylight hours will be shorter. Drying in a controlled outdoor environment or indoors with UV lights can help. Thinning with a small amount of balsam lacquer thinners will also help the curing process.