There are those who keep Sfirah customs even after Lag Baomer, and this is also Minhag Chabad, as seen from our Rabbeim, concerning haicuts etc.
Excerpt from Sicha of Lag Baomer 5746.
Shturem.org thanks Shliach Rabbi Yisroel Vogel for sharing this and other precious gleanings from the Rebbe's Sichos.