I kind of view the sugar babes as a source of variety.  I might see some a few times, but also I see a lot of one and done.  I view it more of a temporary holding pattern than a bench.  And judging by the "regulars" I see frequenting the sugar sites, looks like most expect to have short flings.  
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There's always the next one that I want to do.  It is addicting.

For me the best SR I had was with just one SB where I became a big part of her life for 6 months and great romantic memories together - until one day I messed it up and she ghosted me  

Now I keep a backup in case, but beyond 2, it gets financially very difficult to do them justice even if I want to have that much sex.  

And as Metrik said above, if you are only seeing someone like once a month it is more like an escort situation and I want to stay as far away from that now as possible - I need that emotional angle too to make it fulfilling

"I have two pretty good SBs at the moment" -- and therein lies the conflict. If one of them was amazing, then you would never have written the post.  Lester put it well -- SBs are addicting, whether it is the superb connection with a Unicorn, or the chase to the next M&G.

I have a desire to always look for the next Unicorn, or at least the next SB that really intrigues me.  And that leads to being overextended -- financially and with time constraints.  When I have too many SBs, I am blunt with the one that floats my boat the least -- "I am entering a busy time at work -- are you OK with seeing each other intermittantly?"  Then the choice to leave falls on her.  I am seeing three right now -- one a long-term single mom that is a lot of fun naked, but doesn't really float my boat; one a new beauty that I would like to try to evolve with; and one that is pretty meh, but super easy to deal with.  I am going to have to back off with the last one, if I try to evolve with the second.

But honestly, since none of the three is amazing, I'm on Seeking as we speak chatting up a 22-year-old coed at the university four miles from here...she may be a Unicorn....lol...

My point is, if you are looking for amazing, you need a mindset where you can move on.