My lo also likes to only sleep 45 min. I've come to realize though it's probably cause he tends to get sleepy after about an hour and a half of awake time, so I can't expect for him to have a super long nap. For the past few days, I think he's naturally starting to stay awake longer and is now sleeping longer stretches. How much awake time is your lo getting between naps? How much is sleep at night is he getting?
For us, Cohen started being able to put himself to sleep on his own since about 4 months old. When he seems tired, I now just place him in his crib, give him his blanket, walk out, and I don't hear anything from him. It took a lot of sleep training too, and then one day I just had to let him fuss for him to fall asleep. I knew he wouldn't learn until I just let him sort it out - he tends to get more stimulated when I am in the room. He now rarely ever fusses when I put him to bed. I think that you have to pay close attention to his cues though to make sure he doesn't get overtired, that way he'll fall asleep easier.
Good Luck
Michelle