A staff member who continues to be successful over a long period should be given more opportunities. This person might be willing to share knowledge with new staff members as a mentor. Mentoring opens learning for both the seasoned employee, as well as the newly hired. A strong relationship is formed. Successful mentoring improves morale and increases productivity.
It might also be helpful to ask this employee to help in planning professional development activities. This employee, more than likely has some ides on what needs to be addressed in her areas of expertise.
In one sense, if you have a staff member who has been in a certain position for a long time and performing well at it, you might want to think about the adage "if it ain't broke, don't fix it." Another issue you might want to take into account is the "Peter Principle"; the staff member who is successful in one level at one position may have reached her optimal level of performance and comfort, and grooming her for a higher level position might actually diminish her performance.
One area though from which all staff members can benefit is additional training, especially in new technology. This should be handled delicately, in that you don't want to suggest that her skills are becoming obsolete as a loyal long term employee is one of your business' greatest assets and you do not want her looking at the job market. Instead, offer training as a perk, by seeing if she might be interested in attending a seminar someplace nice (Florida in the winter, for example), which she will see not as a negative comment on her performance but a reward.
Next, you might meet with her and discuss her ambitions for the future. If she is interested in moving up to a position with more responsibility, you can lay out a path which includes assuming more responsibilities and perhaps training in additional skills that could move her to the next level.