second wind - is there a third?

This morning, as I headed out with my son on his week's long run of 9 miles, and with husband Kendall accompanying us on his bike, my legs felt a bit...whupped... I'd run ~10 miles yesterday to/from/with the Boulder Road Runners. The "with" part included 2x8 minutes followed by 30 second pickups. The rest of the day was fairly laid back (weeding, voting, financial planning, prepping for garage sale, yada yada). But the legs were a bit slow on the uptake this a.m. However! About 15 minutes into the run they seemed to wake up (I love when that happens - especially when it's quicker than an hour into the run...my usual second-wind time frame) and I was actually able to keep my son well in sight the first half of the run. During the second half of the run, he backed off the pace a bit and I actually caught up to him. Then he really began to fade (it was becoming rather toasty out there), and the rest of the run was spent running from shade to shade, handing him my water/gatorade bottle, dousing him with water from Kendall's extra supply of water, etc etc. He has since rebounded quite nicely - and I'm wondering just how much spring these legs have left in them for tonight's run to/from Boot Camp. Looking forward to finding out!