well, i think the decision depends on what metrics you tend to take interest in.

if you are interested in weekly stats (average profit, min profit, max profit, etc.), then the lump some will skew the data. if you're tracking monthly or just over time, then i think the lump some is fine.

I don't add bonuses to my roll. Does that make sense?

Bonuses help to move up faster. There is nothing wrong with it. If you are taking money out of your roll every month (my case), why not count bonuses?
The really important factor when moving up is your current win rate at the level you are playing...of course over a significant amount of hands, such as 20-30K.

I pro-rated them across the last 2 weeks - though $720 isn't paid until 18th April I still remain with more than 45 buy-ins for the $200 games so I don't feel like I'm likely to be bust by the time mid-April comes