20min on the breast is quite normal. My dear daughter will drink about 10min from each breast for a normal feeding.
The time my dear daughter spends on the breast depends on her mood and appetite for that feed. If she's sleepy she may suck longer and drink more but if she's tooooo sleepy, she may not suck long at all.
The period of time between each feeding for an older baby may be longer. 5 hours? Not really , unless baby already on semi-solids or is sleeping thru the nite. Feeding time isn't necessarily longer since flow is faster as baby is more expert at getting letdowns. That's at least in my case. Jia you!!!