I use a four-sided strop with diamond pastes (3 to .25) to touch up my razor. I love the feel of the blade after finishing with the .25 side, but I find that the edge doesn't stay as keen as I'd like beyond 10 days. I initially thought I was ruining the edge with my stropping, but I've been extremely careful to keep a tight strop and use a light touch. Any ideas what I'm doing wrong? Or is this edge too fine to be durable?