Yeah, you really have to manage your BR well from the perspective of having it in multiple sites and such in order to get these bonuses. If there's a site that you will get on to play if you know they have a bonus, make sure to keep enough out in order to do it. With most sites like Party, Empire, or Paradise where the bonuses are super easy to clear and you'll always jump on the opportunity to do every one then you really don't need more than $500, presuming they don't all go nuts with a reload at the same time (this does happen semi-frequently, like at Super Bowl time). If you don't want to take all your money out, leave enough for a few buyins. As an example, I had been depositing for every reload at UB and had like $1800 in there and they let you withdraw without losing bonus, so I went ahead and took $1400 out. Good thing too, cause they just had another reload and I dropped $800 more in there.
Once you get a bigger BR you can start leaving your money around other places and maybe play a little here and there so they don't think you're abusing bonuses (if you're an active bonus chaser).
Now, what am I going to do with $1255 in bonus money on UB waiting to be cleared?