Glasses and optics have always intrigued me (should have been an
optometrist) so I'm hoping to get some insight on my prescriptions.

Dr. #1 : January 2003

+0.25 (+0.25 10 degrees)
+0.25 (+0.25 170 degrees)

I didn't get these.  She said not to unless I really needed them.

Dr. #2 - November 2005

+0.00 (+0.25  50 degrees)
-0.25 (+0.25 140 degrees)

She commented that my astigmatism was very unusual and explained why
but of course I didn't understand.  I got the glasses (first time I've
ever had glasses) and they helped but I guess I really didn't need
them cause after a few weeks I stopped using them.

Dr. #1 (same Dr. as 2003) - February 2008

+0.50 (-0.25 110 degrees)
+0.50 (-0.25 70 degrees)

I had been having blurry vision (I work at the computer all day) for
the past 2-3 months and it was finally bothering me.  She said my eyes
haven't changed since the last time she saw me (2003) but my ability
to focus my eyes is weaker and that this time I should get the
glasses.  I didn't mention the fact that I saw Dr. #2 since my last
visit.

I got the glasses and they help a lot.  The text on my monitor is
crystal clear.  I've been wearing them since I got them, about a week
now.  Today I tried on my old glasses for the first time since getting
the new ones.  I see better with them (I'm comparing them while
reading text on the computer) than without, but in my opinion the text
isn't as crisp as it is with my new glasses.  So then I started
googling.  I found out that Dr. 1's new prescription is basically the
same as her old one, with the axis changing slightly (10 degrees for
both eyes).

The first question is what is the tolerance of error for determining
the axis?  Do eyes change 10 degrees over 4 years?

The next question is how did Dr. #2 have totally different axis?  I
would think that if the axis were off by 20-30 degrees it would make a
big difference.  Or maybe my eyes have changed a lot each 2 years?
Unlikely that he'd change and then go back to the way they were
before.

Which leads to the third question: Why did Dr. #1 give me a slight
magnification (+0.25) while Dr. #2 gave me 0?  I only use the glasses
for reading and the computer so I think the magnification is good
right?

And final question, can I still wear my old glasses?  I use my new
ones for the majority of the time but it'd be nice to have my old ones
by my bed for bedtime reading, or for a backup.  I don't want to use
the old ones if it's bad for my eyes.

Thanks for the help in clarifying these prescriptions.