Clangers - I think it is perfectly normal for young babies to behave like yours - almost constant feeding, and awake for long periods in the evening. I think you're right, that it's possibly a combination of overtiredness/overstimulated and build up of wind. Dd1 was like this, dd2 less so. Sounds like your dd sleeps really well at night, and is going for good lengths of time between feeds during the rest of the day, so I'm sure she's fine, and your milk supply is fine. In the evenings there is often less milk, but it is also higher in fat.