I had this (long sleepy feeds, not lip/tongue tie), ESP with dd1.
Rubbing my dds' backs and/or unlatching and latching back on were helpful to keep my dds feeding and not nodding off! Blowing gently on her face could also help sometimes.
Also, if he's taking such long feeds (60 mins?) maybe he never gets really hungry before the next feed. (Maybe the acting hungry is wanting to suck more than actually being hungry?)
Perhaps try stopping the feed after 30-45 mins, say, and seeing if he takes a better feed next time?