I'm waiting on a few (Holly Brisley, Tim Campbell, Kate Ritchie, Bernard Curry, David Jones-Roberts, Sonia Todd, Axle Whitehead, Jodi Gordon, Rebecca Breeds, Cornelia Frances, Esther Anderson, Luke Mitchell, and Todd Lasance) but only sent them a few weeks ago so I'm not expecting replies any time soon... Stefan's not very good at personally replying these days so I shouldn't hold my breath for a response, but saying that I did write to him via Panto last week - at least this way I know it'll go directly to him.
I've personally never re-written to anybody, but I'd say leave it at least six months before re-sending just in case your letter's at the bottom of an ever-growing pile.
Completely disagree with you about Axle but each to their own