Well, now that some of the dust has settled a bit....
pghickster, I don't know if there is a singular answer to your questions. We've got guys that have posted on here that can pound out 80-90 miles a week in singles without a hitch, then we've had others who, while very fast, can't manage more than about 30-35 mpw before some niggle forces them to rest or cross-train. So it's a very individual thing as to what will or will not work for you. I think the main point is to recognize when your body is not ready to handle a hard workout, even if your "plan" calls for one; if it's unusually laborious, it's probably better to back-off and train hard another day. Having that flexibility will steer you clear from going down that rabbit hole (been there, done that.) As to your second point, no, I don't think you're missing anything, and it is a good rigorous schedule that may or may not work for you, as I discussed above. Generally, the muscles and aerobic system will adapt more quickly to an increase in training than the tendons and ligaments will, so it's important as one increases volume and/or intensity to recognize that your body will allow you to increase your training faster than it is really ready to handle. It may take a lot longer than you'd like to be able to increase to a point where you can chronically handle the load to your tendons and ligaments. Just my opinion (your mileage may vary.)
old guy II, nice job on that XC race...I've had the same experience where I've run equal or better when feeling awful...not sure how that goes.
AK-53, yeah, seems some of our recent "regulars" have taken a hiatus. I'm feeling a bit like I've lost a few friends and am hoping that they will reconsider and rejoin the fray. I certainly enjoy reading about our super-fast 50+er's. I know several are training for the National 5k Masters Championships to be held in Syracuse in a couple of weeks (http://www.usatf.org/events/2011/USAMasters5kmChampionships/), and I'd definitely love to know how things are going in the lead-up. I'm pretty sure Pete Magill will be trying to do something special at this race. Curious whether John Tuttle will be joining them, he's not listed as of yet.
Rtype, should have said this in my initial response, but best of luck with the knee. One thing that I found has been working really well for me as I've been rehabbing my knee is to end my easy runs by jogging 100 steps (or 200, depending on how you count them) backwards. I can really feel it working those support muscles that surround the knee. Certainly, being cautious has also helped.
alhoa warrior, there is a lot of wisdom on this thread from the earnest posters. Many have had excellent running careers. There is no doubt that one has to change expectations as one gets older, and in your case, I applaud your tenacity and resilience. Some of life's adversities have clearly placed extra challenges on you that makes every day that you are able to get out the door and hit the pavement a day to be grateful for. Kudos.
Skuj, way back in my youth, as a speedskater, we took long-range periodized training theory very seriously (Diane Holum was our coach), and were taught how essential rest weeks were as we built up our training. We'd back off every fourth week whether we felt the need to or not. It was a integral part of the training schedule and is something that I had adhered to do for two years of increasing distances and improving times (and no injuries). Then I ignored this training habit late last summer and that is when all the trouble started. Not sure how often you back off on your training, but perhaps those couple of tired runs were a signal to take it easy this week....just a thought.
So, over 50 and Desert Rat are both running NYCM...cool.
Really enjoying everyone's posts this week. Cheers.