Long time lurker, first time poster...
I've been in almost exactly the same place you are now. I'd echo a lot of other posters in recommending you stop KEM farming, stop Mystery Box buying, store some Lard Lads, etc. I don't think anyone has mentioned maybe storing some Heights buildings permanently. At your (and my) bonus level, I think this is perfectly reasonable -- the hidden bonus isn't highly beneficial to us anymore.
I know there are psychological barriers to overcome here -- not using the most cost-efficient method of getting donuts! Having premium items in storage! -- so here's how I look at it: I put a lot of grinding into getting my bonus over 2000%. But the bonus itself wasn't the end goal, having plenty of donuts and money was.
And now that I have those, my reward is doing a lot less grinding. And having achieved my goal, I was also eventually able to break free of the notion that if it produces income or has a bonus then it cannot reside in storage. I'm still not totally free of it. I find the Beach Hideaways an eyesore for example, but haven't yet brought myself to putting them away even though the 100% bonus is no big deal to me at this point.
But, on the whole I don't have to grind in my main town anymore, so I don't, aside from setting tasks once a day and collecting income once or twice. No KEMs, no trucks, no vast farms of buildings. Every day I still net around 8-10 million money and around 40-50 donuts (my Collider is always on, and never mind cost efficiency, I always tap for 3 donuts).
