Tips for night potty training my 4y/o?

My sons been potty trained since just over 2, but I’ve kept him in pull ups overnight. A lot of nights he stays dry, but pretty frequently has accidents still. I have no idea how to tackle this but I don’t want to keep buying pull ups and he’s starting to get too big for them as is, he’s 45 lbs and 43 inches so I have to buy the big kid pull ups as he’s outgrown the biggest 4t-5t pull ups, I just feel like with how often he stays dry he might be ready & just need to figure out how to go about it. Or is this too soon? Any experienced mamas on this one?