Quote Originally Posted by OakLeaf View Post
Obviously we're talking about longer and/or warmer weather efforts here - assuming reasonably good overall nutrition, I don't think it's a worry for anyone until you've replaced a couple of liters or so of water.
That's a very good point. In fact, I've wondered several times reading answers how long/hot/fast rides are people talking about, I don't use anything for rides less than about 20 miles unless it's >90 degrees out.