Sapphiregal, congratulations on your c25k success. I hope this is just the beginning of a wonderful life of running for you. May I suggest you check out One Hour Runner and the Bridge to 10K programs....google both for free programs. Developing a base of running for an hour or approximately 6 miles will build you a sufficient base to take you where ever you might want to go. ..... running 5Ks, 10Ks, or even a starting point for half or full marathons......gasp!
Even if all you ever want to run is 3 miles or 30 minutes, having that ability to go a little longer builds your endurance and overall conditioning.
Again, congratulations and good luck!
61 year olds must be out of their minds to run a half marathon followed by a full the next day!