Preparation for practice - should I take tax exams?

I qualified about 25 years ago as an ACA.  I have spent much of my career working in large companies with some exposure to tax issues but this has been a minor part of my job.

As the big half century comes closer I have decided to prepare for my second career as a sole practitioner.  I have plenty of time to get my ducks in a row...perhaps a couple of years.  What should my preparation entail?  In particular I am thinking of training for the Association of Taxation Technicians exams.  Is this worth doing?  Would it stand me in good stead or would it be a waste of time?  With my knowledge (even if it is a little out-of-date) and modern software packages will I have enough fire power to provide a good service to clients?

Thanks in advance for any constructive advice....

Jon