I've just been given 1 ft contours for our whole county, but they are in about 11,000 different feature classes. I've started the process of merging them into fewer feature classes to make it easier to work with them. My question, after I do the merge, should I dissolve the lines by elevation? And if so, do I allow multi-part features? I have many millions of features after doing the merge. Is it better to have fewer but longer features? Thanks.