With proper care, you could get many more years out of her. The first thing I would tell you is to really take care of her joints and muscles. Always make sure you do plenty of stretching out prior to any strenuous tasks. This means:
10-15 minutes of walking, moving up into some bending and counter bending toward the end. Really make her flex and bend her neck. She needs to really warm up her muscles controlling her shoulders and hips.
5-10 minutes of simple jogging, doing some half halts and bending both directions.
Do your work out, but if it is going to be longer than I'd say a half hour take a break to let her walk out and relax those muscles. Old muscles can be stressed easily, you need to give her time to recover.
Once your work out is finished, let her walk out for a good 10-15 minutes so she doesn't get stiff.
A joint supplement would also be a good idea. Depending on how much she has been used, keeping those joints well oiled can really improve her performance. Good luck with her! Hope you get a lot of enjoyment with her.