I would have the decay longer then that myself.
No point, I think - it's already slow enough to make waiting it out the inefficient method.
If I kill a clean ship in a FDL then I end up with Notoriety 1, and a sizable bounty.
I can clear that bounty instantly by attacking a station (at a cost of say 10 million in rebuy depending on loadout). I can then spend maybe 20 minutes doing some basic missions to earn that money back. Or, I can wait an hour and pay it off at IF for less.
With Notoriety 2 or higher then even in a full combat Cutter with a 50 million rebuy it's more time efficient to clear the bounty by dying, then do a bit of high-earning work to get the money back (since there are a lot of way to use a ship that big to earn well over 25M/hour), than it is to wait for it to just wear off.
So long as it stops people going kill-jump to IF-clean-jump back-kill in a short loop, it's enough.