Hi Glen,
As others wrote, you can never have too much bench space but the length is not the only variable. Having a bench against a wall is fine but you may want to reserve space at one or both ends so you can hang work over the end and get at both sides. Don't make it too wide, perhaps 24-28" but also consider you may lose some space with power strips, task lamps, shelving and organizers along the wall.
dave