I find I need to replace my alloy nuts annually, in that time they've probably been on/off up to 50 or 60 times. I've found exactly the same as you when I've failed to do that.
You must always torque alloy nuts, never rattle gun, I elect to go with 80ft/lb.
I also lightly lubricate the threads every third time with "Never Sieze".
I buy mine from Racer Industries, Aussie made ones at about $10- each from memory, much cheaper than the Jap Titanium ones that admittedly, do last longer.