This is an interesting cache and one for which I was fortunate to be FTF.
As Windrush asks in her note, the problem is knowing if you have qualified or not. She has found thousands of caches and obviously can’t remember more than a small percentage of them. I was fortunate in that my qualifying cache was only found a few weeks before. As Windrush has found just about every cache on the moor, there won’t be any qualifying caches for her nearby.
For those who have found less caches, the best option is to identify a qualifying cache and go for it! But there are thousands of caches out there! I can save you the time of checking mine – all have been found within the last 6 months. Difficult puzzles are probably the best option and I bet a couple of MPs haven’t been found for over a year – but you may need his help 🙂