Mine is factory installed

 

2009 sg, never had it happen yet. 10,000 miles.

 

My two cents worth on this is you have an issue with the front brake switch. My '05 did the same thing and finally got to the point that the cruise control did not work at all.
If someone would follow you I would bet they would say your brake light flickers randomly while you ride normally. Test this by setting your cruise sometime and pushing forward on the front brake lever and see if it works better while the pressure is on the lever. Application of the front brake causes cruise control to release.
I ended up CAREFULLY removing the lever and putting a small dab of epoxy & a #4 brass nut (for strength) where the lever touches the brake light switch. There is also a little brass shim that is supposed to be in place behind the brake light switch to push it out a bit. I replaced mine but it did not change anything.

 

Run a diagnostic test and see if it throws a code. Procedure available on the forum, do a search.

 

Cruise will also disconnect if the throttle is rolled forward (off), so even if you don't hit the brakes, and want to disengage, roll the throttle forward and it goes off. Sometimes when hitting bumps, you might just be grabbing enough forward throttle to disconnect in an effort to hold on.

Just thinking.

 

I use the cruise ALL the time, my '08 had 11,000 miles and never turned off and my 09 had 21,000 miles and has never turned itself off.

I do use an extremely light grip on the handlebars.