John Gill Commentary Deuteronomy 12:19

"Take heed to thyself that thou forsake not the Levite as long as thou livest in thy land." — Deuteronomy 12:19 (ASV)

Take heed to yourself that you do not forsake the Levite
By withholding from him the tithes appointed for his maintenance; or rather by neglecting to take him with him in order to partake of the feast or entertainment before spoken of:

as long as you live upon the earth ;
so that it was not one time only, but always; whenever he ate these holy things before the Lord, as long as he lived, he was to be careful he had the Levite with him, for a reason given, (Deuteronomy 12:12) .