I had to re-flock my dressage saddle last year after both my mares gained all those muscles. Thankfully it did seem to be enough. I was thinking about other "spare" saddle as well, but didn't take that route as of yet. As for borrowing you can always ask around, but I doubt too many people will borrow (unless you have a good friend, who doesn't mind).
"Life isn't about waiting for the storm to pass: it's about learning to dance in the rain..."
"When we are no longer able to change a situation - we are challenged to change ourselves."
"How people treat you is their karma; how you react is yours."