Thanks - it's worth listening to your body! I used to run regularly 45 - 50m per week, then in October 2010 became ill. I was unable to train for about a year, then started back, with advice from a "professional". I followed the advice and ended up with an achilles injury (having never had an injury at all following my own instincts in previous years). That took me out for 3 months, so following physio etc, I'm starting back on that plan, taking it very slowly and making sure that I'm not tight afterwards.
By all means keep doing the heel drops during the day, but it would help to do them immediately afterwards.
I also invested in a step platform - I found doing them on the stair at home wasn't totally successful due to the carpet, so decided to invest in one - it only cost £20, but was worth it.
I also do calf stretches, presume you do too and, when out, try as much as possible to avoid hills. It's fairly steep where I live and I can't get home without going up a number of smallish hills, but if it's going to be too much, then I slow right down and will, if necessary, walk, rather than incur another injury.
I know hill training is recommended, but I'm going to give it a miss. My legs are older than yours and they were working perfectly well until this idiot gave me a stupid programme. I should have followed my instincts and not done it, so in a way, serves me right.