[john kane]

the original poster has exactly the same thoughts as me. i agree with him.

you do not have 500BB if you are never going to use 300BB at the same level. you have 200BB at say 10-20 and 600BB at 5-10. That is the way you should be viewing your bankroll if you are going to move down limits when you lose 200BB of your 500BB. you are never going to be playing with the remaining 300BB at 10-20 so it is pointless viewing it as such.
Instead you should always be viewing your current level as risk money (in this example 200BB at 10-20) and if you lose it you can then drop down to 600BB at 5-10.

if you are saying you are going to move down whenever you lose a set amount, you do not have a bankroll, merely you are slowing the swings you experience.

for example, you could easily have a bankroll of $200 and play 2-4, ie 50BB. if you drop to $100 you move down to $1-2, if you drop again to $50 you play at $0.50-$1.

here you are playing with a 50BB bankroll and have a 0% risk of ruin as you will always have a bankroll. The reason for having such a large bankroll say 500BB is so you dont have to move down limits and constantly have swings, you want to be playing a set limit until you have won enough to move up.

players should either have a 50BB limit or a 1000BB limit imo. the 50BB bankroll means you are constantly going up and down, but have a 0% risk of ruin, the 1000BB means you never have to move down limit and can slowly progress.