I would like to place a challenge cache, where the geocacher is activ for at least 10 years. In my case I started in 2009 and I have found 10 years in a row caches. It's not important how old are these caxhes are, only that a cacher is active the last 10 years.
I believe that such a challenge is not allowed under the current rules. The reviewer will see this as a streak of 10 years although it is one cache per year only. The rule is that a streak should not be longer then 1 year.
But please check with your reviewer if he would publish your challenge.