Skip the ride?

[RhndLev@cs.com]

Okay, I need some experienced people's opinions here.  As you all may or may 
not remember, I ride an 11 year old TWH mare.  Prior to my purchase of her in 
the fall one and a half years ago, she was ridden on multi-day rides in the 
Ozarks and did some Competitive Trail rides with a local group there.  She 
was in great condition when I purchased her and could do a 25 mile easily 
with excellent recoveries.  However, the next spring, I injured my knee and 
then she had a minor injury to her knee and we rode a grand total of four 
times all last summer and fall.  This year, we were staying on a conditioning 
schedule a little better, and have done one 15 mile CTR, one 40 mile CTR 
(over two days) and a 25 mile AERC ride.  However, in the last three weeks, 
I've only had time to ride her once for 12 miles.  Between two children, four 
years and six years, chicken pox, and full time work, I just haven't had any 
time to even lunge her.

So, my question is, how fast do horses lose condition?  Is it safe to take 
her out on a 25 mile ride on June 16?  And if so, what should be our riding 
schedule between now and then?

Rhonda