I had 10 mg 3 times a day in the 1990s for 3 weeks, seeing my GP weekly. Then down to 5mg x 2 days. Than as necessary. I knew that 5mg was enough and would work so there was never any worry about requiring more, even though I knew it was OK to take up to 15mg a day.
It mayB that you need a different betablocka? 27 years is a long while, do U get a regular review?