Definately keep at it. I used to belong to a Life Saving club where one of the members, in her late 50s to early 60s at the time, had learnt to swim about 5 years before I got to know her. When I knew her she had just passed her Lifesaving Award of Merit and was working toward her Distinction, the highest award the RLSS gave at the time. So you are never too old!
Wow, thats a fantastic achievement!
I do 40 lengths (25m pool) 3 days a week now. I'm slow as hell (ca. 30mins) but reasonably steady. Trying to convince myself to increase the lengths but I get a bit bored by the end of the session .
What I'm really trying to concentrate on now is stroke improvement. I do 20-21 per 25m but I know that's not great so I'm trying to reduce that.