Why don't you approach all the TNSS clubs with logo designs? You seem to have a bit of a grip of which clubs/comps need progressive logos and which need ones which require a historic element.
Surely you have some possible designs going for all Aus teams (Super Rugby & Wallabies), possibly with the exception of Rebels... I for one like seeing your designs so post away!!
As a general thought, how long should professional teams hang onto logos? American sports rarely change, European sports seem to be very traditional and rarely change; AFL are reticent to change but NRL (and to a smaller extent, Super Rugby) change a bit more regularly...
I am Approaching a few with logos in fact, and a few clubs in queensland Im designing for in the hopes one day they get into the Hospital Cup.
I have designs for the rebels, not much else because I think the current ones are good. Wallabies don't need one either, 7's team does though which I have.
It depends on the style of design. Traditional crests etc should always stay with eternity, maybe with slight updates adding a modern section to them. Modern/progressive ones rarely last more than 10 years without adjustment, though some last that time as the end up falling into a traditional image (ie the wallabies only would require slight mods in about 10 years). American sports change more than you would actively notice in the NBL, NFL and NHL, the MLB are more or less text type logos and therefore don't require it, as the image is based on a twinning of the word and font. AFL are smart in putting out their old logos with new ones used in duality. NRL has americanised too much for my liking, rely too much on the mascot rather than the tradtion, which requires change, as images complex in nature require multiple modifications.