Thanks for all the feedback, running gals! I can run about 5 miles max, though I haven't done that much for awhile. I generally only run for about 40-45 minutes, so I'm only getting 10-15 minutes of the "high", but it's really nice when it comes!

I would like to run longer, but most of my runs are done at our work gym on the treadmill, and time is limited. I am not very good at outdoor runs because it's usually either too cold or too hot for me -- I am very much a wimp when it comes to running and temperature zone. I don't ride in very cold temps either, but I will ride in hot temps b/c of the wind I create. That doesn't happen w/running, so I get uncomfortably miserable too fast.

Don't know about the age thing -- I will be 50 next month, and blessedly, it doesn't take me quite that long to warm up either running or on the bike.