2 days
Fort William, not the summit
A bed in town, the glen under Ben Nevis, and the distillery at Lochy Bridge. The summit can wait.
The town is the base. The mountain is a full day, and it has strong opinions about being rushed.
Day one. Walk Glen Nevis. The visitor centre is the start. The lower falls are further up the road. Come back to Fort William for the night. Ben Nevis Bar is on the High Street, with a terrace over the loch. Same famous name, different building.
Day two. Ben Nevis Distillery is at Lochy Bridge, on the north edge of town. Book it for the end of the day, then stay in town. The glen will keep.
The summit and the tour are two diary entries. Ben Nevis does not do “while we are here”.