Back Calculating Power Numbers

So with all the power training gurus on this site, I'd thought I would pose this question. What are the advantage/disadvantages of creating your own power/time cuve for those of us that do not own a power meter. Bascially I'm interested in pacing for riding longer distances. What I've done is looked at my training logs, taken the max average speeds (avg=source of error) for basically flat rides of given times, plugged the numbers into kreuzotter.de and graphed the results. It is important to note that this is REAL WORLD data (effected by things like traffic and wind), not lab data. For shorter distances/times, I've measured some and guesstimated some. I would guess that my short times are underestimations (they are all lower than the curve), as I've based them off avg speed held over a given time.

How can I use this to help me, or is it a waste of time?

I don't have huge numbers, but being smaller (approx 140 lbs) I can get away with lower numbers. I do FEEL like I'm riding stong as of late.

Thanks in advance,
L

 

For relatively flat courses, I don't know why you couldn't use the curve to estimate your max speed (with adjustment for wind). For example, to plan speeds for a flat century. For hills, it wouldn't be of much value because the speeds are so affected by the grades.