You've been playing in the $1 SNG for eons and suddenly you hit it big time in one of those freerolls.  Your bankroll is several times bigger now allowing you to play in $3 or $5 level.  Do you jump in immediately.  One way to test the water is to do the Cowboy challenge (which is quite popular here in PSO).  You allocate some of your bankroll that will allow you certain number of buy-ins.  Let's say 20 buyins for $3 SNG is $60.  In the true sense of the Cowboy challenge, your objective is to double your $60 after 100 games of $3 SNG.  

You fail of course if you lost all $60 or decide not to continue.  Well at least you did not lose all your bankroll and you can still continue playing in the $1 level, until such time you feel you are ready to do another Cowboy challenge.  

If you managed to complete 100 games but did not double your buyin, it will still give you something to evaluate your game and you can decided to continue or not.

Cowboy challenge is a good form of bankroll management.  You allocate portion of bankroll which you are comfortable to part with.  And it gives you specific indication when to stop and move back down to your current level.

I am currently doing a $3.5 SNG Cowboy challenge and you can check my progress here: http://www.pokerschoolonline.com/forum/showthread.php?55783-Going-for-Silver...&p=456869#post456869