If it were me, I would stagger planting so as to have a continual supply of lettuce to provide to my customer. It make take a couple of cycles to figure out the stagger but lettuce is a very short cycle plant so it won't take too long.

Thanks Grizzman. I was also wondering if anyone knew how commerical farms do it. I mean how come they, whether hydro farms or soil-based, have supplies extending year round. Does it only boil down to having a large area for planting?

I saw a youtube video one of a commercial lettuce operation. basically, the sprouts and small plants don't need near the space as the full size plants. so you put them in a plug that can be moved from one raft to another.
Try searching around there and I think you'll find what you're after . try searching youtube for commercial lettuce hydroponics raft

Grizzman, thanks for your prompt reply. I tried watching some videos on youtube after reading your post above, and what I've seen thus far are setups in nft. Could I ask for the link that had a raft system?

One suggestion is to determine how long it takes to grow the crop(weeks) then divide your total plant capacity by the # of weeks it takes. The result is the # of plants to start each week. For example... If it takes 10 weeks for lettuce to grow and your system holds 80 plants, then you would want to start 8 new plants each week (and harvest 8 plants). It gets more complicated with other factors(e.g. Light, temp) but this could be a starting point.

Sdgrower - Thank you so much for the detailed response. Such a big help!