After a crown lengthening procedure how long until my gums are well healed?

A few days. Gingival tissues heal very quickly and you should be feeling pretty good after just a few days. Doesn't mean you can eat hard foods in that area right away though.
Define "Well" Depends on what you mean by "well." they'll look pretty good in about 2 - 3 weeks. However, if you're going to have a crown or bridge placed onto such a tooth (especially if it's visible when you talk/smile), it won't be adequately healed for at least 6 - 8 weeks. If you aren't in a hurry, it would be even better to wait 12 weeks before doing any cosmetic dentistry on that tooth. Then you're safe.