Cut and come again lettuce.

Is there a way to allow lettuce leaves to regrow without the stem going brown wherever the previous leaves used to be? I'd really like to have fresh lettuce on hand whenever needed but I find this problem occurs no matter what the lettuce species. I've heard some people use a knife to harvest the leaves. Does that prevent the stem going brown?

The stem will always go brown that is why you need to cut pretty close to the crown. Then cut above the brown tips.  I used to know the distance from the crown, you can also try and gauge it by saving the newest little leaves on the crown.

One site says to cut about an inch from the base. Will the remainder of those leaves die or continue growing?

I think 3/4 of an inch is the measure I used to use.  The cut leaves pretty much stay where they are.  The new leaves from the crown is what you will cut next, so if you do not cut close enough to the crown it is hard to avoid the brown tips you are talking about.   You can also hold the new leave you are going to cut/harvest and when you cut with a knife or scissor athe small brown tips will fall on the ground.