You don't need to grow them inside for 6-8 weeks. You can plant them out as soon as your weather allows and you feel they are big enough (i.e. 3 or 4 sets of leaves, 4-6 inches tall, won't wither up without constant watering or if a strong wind comes along). That said, assuming you keep your lights close enough, they won't get out of hand before you plant out; they won't grow faster than their roots will let them. I have some that I started in February; they're a little leggy, as I ran out of space under my lights and they've only had sunlight for the past week or so, but they are still probably only 6 inches tall.

They will grow faster with each set of new leaves. They don't do that well inside unless you keep your house on the cool side. They are cool weather growers doing best in spring and fall IMO but should do better in summer in your zone.