As I understand de khatm-an-nabiyin is not the end of revelation, but the end of Menssengers of a revelation. God can reveal whatever or however H pleases to any ody today and ever, bu the mission of transmitting a revelation to mankind is not necessary for those who have accepted the Coranic revelation. Of course, anybody can speak of whatever has been revealed to him or her if God has not forbidden it, but there is no absolute need or obligation, or may be personal or for particular purposes.
In that sense, I suppose there are no limits for the number of lailat-ul-qadars. There may be personal lailat-ul-qadars.