This is a question that we see here a lot. The only good answer is, "it depends". Everyone is different, and every trail is also different. I and my hiking partners (all in our 50's and hiking in the Sierra Nevada) figure on 1 to 1.5 miles an hour. That includes lots of picture stops and lunch. Given this figure we shoot for about 8 miles a day max. However, we have done 12 plus miles to avoid known bear problems (downhill of course). We are possibly three of the slowest hikers around, but it works for us. Your job is to find out what works for you. That is the only way to know.

ken