I went to Camp Longhorn (near Burnet) for four years as a camper and four as a counselor. Sent my kids there too, starting around 2010. Camp Champions is probably similar. Camp Longhorn has three camps, Inks Lake is the original, Indian Springs was the second, and they have a C3 camp on Inks with shorter terms.
Inks Lake and Indian Springs offer two and three week terms. When you are young, three weeks is a long time to be away from home. But when you are older, you don't want it to end.
Terms at the start of the summer are going to be cooler but the water is going to be colder. The terms towards the end of the summer can be really hot but the water is warmer.
I also did a Scouting trek at Philmont when I was 15. At Philmont, you are part of a crew that hikes from camp to camp for about 10 days. I think we covered about 65 miles but I can't remember. My troop had a qualifying hike that you had to pass before you could sign up. I wasn't ready at thirteen. Two years later the qualifier was easy, and Philmont was a challenge but doable and I'm glad I waited.