Here's a 30 min challenge to do every day.
Start at 40 and see how many finishes you can get in 30 mins
Next day start at 60
Next day start at what ever you finished at e.g. 76
Etc, etc
Start fresh each week or when you can't hit a finish in 30 mins.

I keep a record of my highest finish and have 10 walks at it a couple of times a week, currently at 131.
When you get into the high finishes try to leave 40 or 32 if you can't get the big one!

Another good one mate! keep em coming